diff --git a/lib/Checkout/Accounts/AccountsClient.php b/lib/Checkout/Accounts/AccountsClient.php
index 016bc4f..fe909ff 100644
--- a/lib/Checkout/Accounts/AccountsClient.php
+++ b/lib/Checkout/Accounts/AccountsClient.php
@@ -163,10 +163,13 @@ public function updateBankPaymentInstrumentDetails(
         $instrumentId,
         UpdatePaymentInstrumentRequest $instrumentRequest
     ) {
+        // The API reads the ETag only from the If-Match HTTP header and answers 428 without it, so the
+        // request's headers are sent as HTTP headers.
         return $this->apiClient->patch(
             $this->buildPath(self::ACCOUNTS_PATH, self::ENTITIES_PATH, $entityId, self::PAYMENT_INSTRUMENTS_PATH, $instrumentId),
             $instrumentRequest,
-            $this->sdkAuthorization()
+            $this->sdkAuthorization(),
+            $instrumentRequest->headers
         );
     }
 
diff --git a/lib/Checkout/Accounts/AdditionalDocument.php b/lib/Checkout/Accounts/AdditionalDocument.php
new file mode 100644
index 0000000..1be1b17
--- /dev/null
+++ b/lib/Checkout/Accounts/AdditionalDocument.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * Additional space for documents to be provided when requested. Carries a file ID only; the API
+ * defines no document type for it.
+ */
+class AdditionalDocument
+{
+    /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
+     */
+    public $front;
+}
diff --git a/lib/Checkout/Accounts/ArticlesOfAssociation.php b/lib/Checkout/Accounts/ArticlesOfAssociation.php
index b76ed61..6aca229 100644
--- a/lib/Checkout/Accounts/ArticlesOfAssociation.php
+++ b/lib/Checkout/Accounts/ArticlesOfAssociation.php
@@ -3,17 +3,26 @@
 namespace Checkout\Accounts;
 
 /**
- * Memorandum or articles of association document.
+ * Memorandum or Articles of Association document.
  */
 class ArticlesOfAssociation
 {
     /**
+     * The type of document used.
+     * [Required]
+     * Enum: "memorandum_of_association", "articles_of_association"
+     *
      * @var string value of ArticlesOfAssociationType
      */
     public $type;
 
     /**
-     * @var string the ID of the front side of the document, as returned when the file was uploaded
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
      */
     public $front;
 }
diff --git a/lib/Checkout/Accounts/BankVerification.php b/lib/Checkout/Accounts/BankVerification.php
index 50f7ccd..40bd884 100644
--- a/lib/Checkout/Accounts/BankVerification.php
+++ b/lib/Checkout/Accounts/BankVerification.php
@@ -8,12 +8,21 @@
 class BankVerification
 {
     /**
+     * The type of document being used as bank verification.
+     * [Required]
+     * Enum: "bank_statement"
+     *
      * @var string value of BankVerificationType
      */
     public $type;
 
     /**
-     * @var string the ID of the front side of the document, as returned when the file was uploaded
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
      */
     public $front;
 }
diff --git a/lib/Checkout/Accounts/CertifiedAuthorisedSignatory.php b/lib/Checkout/Accounts/CertifiedAuthorisedSignatory.php
new file mode 100644
index 0000000..69e8a20
--- /dev/null
+++ b/lib/Checkout/Accounts/CertifiedAuthorisedSignatory.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * Certified authorised signatory document. Required when the legal representative or other role
+ * owner is not registered on the certificate of incorporation.
+ *
+ * Belongs on company.representatives[].documents (see RepresentativeDocuments), never on the
+ * top-level request documents. Used by the EEA, GB and US company variants.
+ */
+class CertifiedAuthorisedSignatory
+{
+    /**
+     * The type of document.
+     * [Required]
+     * Enum: "power_of_attorney"
+     *
+     * @var string value of CertifiedAuthorisedSignatoryType
+     */
+    public $type;
+
+    /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
+     */
+    public $front;
+}
diff --git a/lib/Checkout/Accounts/CertifiedAuthorisedSignatoryType.php b/lib/Checkout/Accounts/CertifiedAuthorisedSignatoryType.php
new file mode 100644
index 0000000..5f37119
--- /dev/null
+++ b/lib/Checkout/Accounts/CertifiedAuthorisedSignatoryType.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * The document type accepted as a representative's certified authorised signatory document when
+ * onboarding a sub-entity (EEA, GB and US company variants, Accounts API v3.0).
+ */
+class CertifiedAuthorisedSignatoryType
+{
+    public static $power_of_attorney = "power_of_attorney";
+}
diff --git a/lib/Checkout/Accounts/CompanyVerification.php b/lib/Checkout/Accounts/CompanyVerification.php
index 57e9564..bb82714 100644
--- a/lib/Checkout/Accounts/CompanyVerification.php
+++ b/lib/Checkout/Accounts/CompanyVerification.php
@@ -2,13 +2,28 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * The document to use to confirm the company's identity (certified by a power of attorney within
+ * the last 3 months).
+ */
 class CompanyVerification
 {
     /**
+     * The type of document used for company verification.
+     * [Required]
+     * Enum: "incorporation_document", "articles_of_association"
+     * (articles_of_association is accepted on the US Company (2.0) variants only)
+     *
      * @var string value of CompanyVerificationType
      */
     public $type;
+
     /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
      * @var string
      */
     public $front;
diff --git a/lib/Checkout/Accounts/CompanyVerificationType.php b/lib/Checkout/Accounts/CompanyVerificationType.php
index 0d316ae..a80a950 100644
--- a/lib/Checkout/Accounts/CompanyVerificationType.php
+++ b/lib/Checkout/Accounts/CompanyVerificationType.php
@@ -2,6 +2,13 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * The document types accepted as company verification when onboarding a sub-entity.
+ *
+ * incorporation_document is accepted on every variant that takes company_verification;
+ * articles_of_association only on the US Company (2.0) variants. The articles of association
+ * sent as their own document use ArticlesOfAssociationType instead.
+ */
 class CompanyVerificationType
 {
     public static $incorporation_document = "incorporation_document";
diff --git a/lib/Checkout/Accounts/ContactDetails.php b/lib/Checkout/Accounts/ContactDetails.php
index d2fd098..938f0e7 100644
--- a/lib/Checkout/Accounts/ContactDetails.php
+++ b/lib/Checkout/Accounts/ContactDetails.php
@@ -4,15 +4,37 @@
 
 use Checkout\Common\Phone;
 
+/**
+ * Contact details of the sub-entity.
+ */
 class ContactDetails
 {
     /**
+     * The phone number of the sub-entity.
+     * [Required] for every Accounts API v2.0 variant and the US ISV Seller variants; [Optional]
+     * for the other v3.0 variants.
+     * On v3.0, country_code is required and is the ISO 3166-1 alpha-2 country where the number is
+     * registered (for example "FR"), not the dialling code. v2.0 takes number only.
+     *
      * @var Phone
      */
     public $phone;
 
     /**
+     * Email addresses for this sub-entity.
+     * [Required] for every Accounts API v2.0 variant and the US ISV Seller variants; [Optional]
+     * for the other v3.0 variants.
+     *
      * @var EntityEmailAddresses
      */
     public $email_addresses;
+
+    /**
+     * The details of the user responsible for onboarding the sub-entity.
+     * [Required] in the hosted onboarding invite request; [Optional] in the full and lite onboarding
+     * variants; not part of the US ISV Seller variants.
+     *
+     * @var Invitee
+     */
+    public $invitee;
 }
diff --git a/lib/Checkout/Accounts/Document.php b/lib/Checkout/Accounts/Document.php
index 75dbd19..e1d2134 100644
--- a/lib/Checkout/Accounts/Document.php
+++ b/lib/Checkout/Accounts/Document.php
@@ -2,19 +2,38 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * An identity document, as used for identity_verification on the representative (Accounts API
+ * v3.0) or on the top-level documents of the sole trader variants (Accounts API v2.0).
+ */
 class Document
 {
     /**
-     * @var string value of DocumentType
+     * The type of document used for identity verification.
+     * [Required]
+     * Enum: "passport", "national_identity_card", "driving_license", "citizen_card",
+     * "residence_permit", "electoral_id"
+     *
+     * @var string value of \Checkout\Common\DocumentType
      */
     public $type;
 
     /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
      * @var string
      */
     public $front;
 
     /**
+     * The ID of the back side of the document as represented within Checkout.com systems.
+     * [Optional]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
      * @var string
      */
     public $back;
diff --git a/lib/Checkout/Accounts/EntityEmailAddresses.php b/lib/Checkout/Accounts/EntityEmailAddresses.php
index 61acb48..a834b38 100644
--- a/lib/Checkout/Accounts/EntityEmailAddresses.php
+++ b/lib/Checkout/Accounts/EntityEmailAddresses.php
@@ -2,10 +2,27 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * Email addresses for this sub-entity, sent as contact_details.email_addresses.
+ */
 class EntityEmailAddresses
 {
     /**
+     * The main email address for this sub-entity.
+     * [Required]
+     * Format: email
+     *
      * @var string
      */
     public $primary;
+
+    /**
+     * The email address of the person responsible for PCI compliance at this sub-entity.
+     * [Required] for the US ISV Seller Company (3.0) and US ISV Seller Sole Trader (3.0) variants,
+     * together with primary; not part of the other variants.
+     * Format: email
+     *
+     * @var string
+     */
+    public $pci_compliance_contact;
 }
diff --git a/lib/Checkout/Accounts/FinancialStatements.php b/lib/Checkout/Accounts/FinancialStatements.php
index e958884..2b6a6e4 100644
--- a/lib/Checkout/Accounts/FinancialStatements.php
+++ b/lib/Checkout/Accounts/FinancialStatements.php
@@ -2,14 +2,29 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * Audited or management-prepared financial statements (when applicable). US ISV Seller variants.
+ *
+ * Not the same document as FinancialVerification, whose type is the singular
+ * financial_statement.
+ */
 class FinancialStatements
 {
     /**
+     * The type of document.
+     * [Required]
+     * Enum: "financial_statements"
+     *
      * @var string value of FinancialStatementsType
      */
     public $type;
 
     /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
      * @var string
      */
     public $front;
diff --git a/lib/Checkout/Accounts/FinancialStatementsType.php b/lib/Checkout/Accounts/FinancialStatementsType.php
index e854b0d..e0f37d3 100644
--- a/lib/Checkout/Accounts/FinancialStatementsType.php
+++ b/lib/Checkout/Accounts/FinancialStatementsType.php
@@ -2,6 +2,13 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * The document type accepted as financial statements when onboarding a sub-entity (US ISV Seller
+ * variants).
+ *
+ * Note the plural financial_statements. It is a different enum from FinancialVerificationType,
+ * whose value is the singular financial_statement and which belongs to a different document.
+ */
 class FinancialStatementsType
 {
     public static $financial_statements = "financial_statements";
diff --git a/lib/Checkout/Accounts/FinancialVerification.php b/lib/Checkout/Accounts/FinancialVerification.php
new file mode 100644
index 0000000..e68ee1c
--- /dev/null
+++ b/lib/Checkout/Accounts/FinancialVerification.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * Financial statement document. Becomes mandatory depending on the answer provided for
+ * annual_processing_volume; the sub-entity's status changes to requirements_due when it is
+ * needed.
+ */
+class FinancialVerification
+{
+    /**
+     * The type of the file.
+     * [Required]
+     * Enum: "financial_statement"
+     *
+     * @var string value of FinancialVerificationType
+     */
+    public $type;
+
+    /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
+     */
+    public $front;
+}
diff --git a/lib/Checkout/Accounts/FinancialVerificationType.php b/lib/Checkout/Accounts/FinancialVerificationType.php
new file mode 100644
index 0000000..baf4068
--- /dev/null
+++ b/lib/Checkout/Accounts/FinancialVerificationType.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * The document type accepted as financial verification when onboarding a sub-entity (EEA Company,
+ * Accounts API v2.0).
+ *
+ * Note the singular financial_statement. It is a different enum from FinancialStatementsType,
+ * whose value is the plural financial_statements and which belongs to a different document.
+ */
+class FinancialVerificationType
+{
+    public static $financial_statement = "financial_statement";
+}
diff --git a/lib/Checkout/Accounts/Headers.php b/lib/Checkout/Accounts/Headers.php
index ab02bfb..79f223a 100644
--- a/lib/Checkout/Accounts/Headers.php
+++ b/lib/Checkout/Accounts/Headers.php
@@ -5,8 +5,8 @@
 class Headers
 {
     /**
-     * Value for the If-Match header, used to identify a specific version of a
-     * reserve rule to update (for example "Y3Y9MCZydj0w"). Etag.
+     * Value for the If-Match header: the ETag of the reserve rule or payment instrument to update
+     * (for example "Y3Y9MCZydj0w"), sent as the If-Match HTTP header.
      *
      * @var string
      */
diff --git a/lib/Checkout/Accounts/Identification.php b/lib/Checkout/Accounts/Identification.php
index c5c6349..d44d4b1 100644
--- a/lib/Checkout/Accounts/Identification.php
+++ b/lib/Checkout/Accounts/Identification.php
@@ -2,15 +2,29 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * The identification of a representative or individual on the Accounts API v2.0 US variants.
+ */
 class Identification
 {
     /**
+     * Social Security Number (SSN), or Individual Taxpayer Identification Number (ITIN) for
+     * non-US citizens.
+     * [Required]
+     * ^\d{9}$
+     * Length: 9 characters
+     *
      * @var string
      */
     public $national_id_number;
 
     /**
+     * Not defined by the Accounts API: the identification object carries national_id_number only.
+     * Retained so existing code keeps compiling; the API does not read it.
+     *
      * @var Document
+     * @deprecated Not part of any Accounts API schema. On v3.0, send identity documents through
+     *             RepresentativeDocuments::$identity_verification.
      */
     public $document;
 }
diff --git a/lib/Checkout/Accounts/Invitee.php b/lib/Checkout/Accounts/Invitee.php
new file mode 100644
index 0000000..b6323e6
--- /dev/null
+++ b/lib/Checkout/Accounts/Invitee.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * The details of the user responsible for onboarding the sub-entity.
+ */
+class Invitee
+{
+    /**
+     * The main email address for this sub-entity. Despite the spec's wording, this is the address
+     * of the invitee, the user responsible for onboarding the sub-entity.
+     * [Required] in the hosted onboarding invite request; [Optional] in the full and lite onboarding
+     * variants; not part of the US ISV Seller variants.
+     * Format: email
+     *
+     * @var string
+     */
+    public $email;
+}
diff --git a/lib/Checkout/Accounts/OnboardSubEntityDocuments.php b/lib/Checkout/Accounts/OnboardSubEntityDocuments.php
index 0af3ba8..0d29e53 100644
--- a/lib/Checkout/Accounts/OnboardSubEntityDocuments.php
+++ b/lib/Checkout/Accounts/OnboardSubEntityDocuments.php
@@ -5,111 +5,127 @@
 /**
  * The documents supplied to onboard a sub-entity. Which documents are required depends on the
  * sub-entity's region and business type (see the Accounts API onboarding schema variants).
+ *
+ * This is the top-level request documents object. The API ignores keys it does not recognise here
+ * rather than rejecting them, so a misplaced document is dropped silently. The representative's
+ * own documents (proof_of_residential_address, proof_of_registration,
+ * certified_authorised_signatory) do not go here: set them on Representative::$documents, using
+ * RepresentativeDocuments.
  */
 class OnboardSubEntityDocuments
 {
     /**
-     * Identity verification document.
-     * [Optional]
+     * The document to use to confirm the individual's identity.
+     * [Required] for the six sole trader variants of Accounts API v2.0 (EEA, GB and US, Full and
+     * Lite), the only variants that take it at this level. On v3.0 it belongs on
+     * Representative::$documents instead.
      *
      * @var Document
      */
     public $identity_verification;
 
     /**
-     * Company verification document.
-     * [Optional]
+     * The document to use to confirm the company's identity (certified by a power of attorney
+     * within the last 3 months).
+     * [Required] for EEA Company Full (2.0 and 3.0) and GB Company Full (2.0); [Optional] for the
+     * other company variants and the US ISV Seller variants.
      *
      * @var CompanyVerification
      */
     public $company_verification;
 
     /**
-     * Tax verification document.
-     * [Optional]
+     * IRS-issued Employer Identification Number document used to verify the entity's tax
+     * identification.
+     * [Optional] (US Company variants and the US ISV Seller variants only)
      *
      * @var TaxVerification
      */
     public $tax_verification;
 
     /**
-     * Memorandum or articles of association document.
-     * [Optional] (required for the company full onboarding variants)
+     * Memorandum or Articles of Association document.
+     * [Required] for EEA and GB Company Full (3.0); [Optional] for US Company Full (3.0) and the
+     * US ISV Seller variants.
      *
      * @var ArticlesOfAssociation
      */
     public $articles_of_association;
 
     /**
-     * Shareholder structure document.
-     * [Optional] (required for the company full onboarding variants)
+     * Shareholder structure chart (including % of shares) certified by a competent authority
+     * individual and dated within the last 3 months.
+     * [Required] for EEA and GB Company Full (3.0); [Optional] for US Company Full (3.0) and US ISV
+     * Seller Company (3.0).
      *
      * @var ShareholderStructure
      */
     public $shareholder_structure;
 
     /**
-     * Bank verification document: a document showing transactions from the last 3 months.
-     * [Optional] (required for the EEA, GB and US company and sole trader full onboarding
-     * variants)
+     * A document showing transactions from the last 3 months.
+     * [Required] for EEA Company Full (3.0) and the EEA, GB and US Sole Trader Full (3.0) variants;
+     * [Optional] for GB and US Company Full (3.0) and EEA Company Full and Lite (2.0).
      *
      * @var BankVerification
      */
     public $bank_verification;
 
     /**
-     * Financial statements document.
-     * [Optional]
+     * Audited or management-prepared financial statements (when applicable).
+     * [Optional] (US ISV Seller variants only)
      *
      * @var FinancialStatements
      */
     public $financial_statements;
 
     /**
-     * Financial verification document.
-     * [Optional]
+     * Financial statement document. Becomes mandatory depending on the answer provided for
+     * annual_processing_volume; the sub-entity's status changes to requirements_due when it is
+     * needed.
+     * [Optional] (EEA Company Full and Lite (2.0) only)
      *
-     * @var Document
+     * @var FinancialVerification
      */
     public $financial_verification;
 
     /**
-     * Proof of principal address document.
-     * [Optional]
+     * Proof of the company's principal place of business.
+     * [Optional] (EEA, GB and US Company Full (3.0) and the US ISV Seller variants)
      *
-     * @var Document
+     * @var ProofOfPrincipalAddress
      */
     public $proof_of_principal_address;
 
     /**
-     * Proof of legality document.
-     * [Optional]
+     * A regulatory licence document required for the company to operate (when applicable).
+     * [Optional] (EEA, GB and US Company Full (3.0) and the US ISV Seller variants)
      *
-     * @var Document
+     * @var ProofOfLegality
      */
     public $proof_of_legality;
 
     /**
-     * Additional supporting document.
-     * [Optional]
+     * Additional space for documents to be provided when requested.
+     * [Optional] (EEA, GB and US Company and Sole Trader Full (3.0); not the US ISV Seller variants)
      *
-     * @var Document
+     * @var AdditionalDocument
      */
     public $additional_document1;
 
     /**
-     * Additional supporting document.
-     * [Optional]
+     * Additional space for documents to be provided when requested.
+     * [Optional] (EEA, GB and US Company and Sole Trader Full (3.0); not the US ISV Seller variants)
      *
-     * @var Document
+     * @var AdditionalDocument
      */
     public $additional_document2;
 
     /**
-     * Additional supporting document.
-     * [Optional]
+     * Additional space for documents to be provided when requested.
+     * [Optional] (EEA, GB and US Company and Sole Trader Full (3.0); not the US ISV Seller variants)
      *
-     * @var Document
+     * @var AdditionalDocument
      */
     public $additional_document3;
 }
diff --git a/lib/Checkout/Accounts/ProofOfLegality.php b/lib/Checkout/Accounts/ProofOfLegality.php
new file mode 100644
index 0000000..bbc22a3
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfLegality.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * A regulatory licence document required for the company to operate (when applicable).
+ */
+class ProofOfLegality
+{
+    /**
+     * The type of document used for proof of legality.
+     * [Required]
+     * Enum: "proof_of_legality"
+     *
+     * @var string value of ProofOfLegalityType
+     */
+    public $type;
+
+    /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
+     */
+    public $front;
+}
diff --git a/lib/Checkout/Accounts/ProofOfLegalityType.php b/lib/Checkout/Accounts/ProofOfLegalityType.php
new file mode 100644
index 0000000..4142f56
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfLegalityType.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * The document type accepted as proof of legality when onboarding a sub-entity (company
+ * variants, Accounts API v3.0).
+ */
+class ProofOfLegalityType
+{
+    public static $proof_of_legality = "proof_of_legality";
+}
diff --git a/lib/Checkout/Accounts/ProofOfPrincipalAddress.php b/lib/Checkout/Accounts/ProofOfPrincipalAddress.php
new file mode 100644
index 0000000..4acae33
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfPrincipalAddress.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * Proof of the company's principal place of business.
+ */
+class ProofOfPrincipalAddress
+{
+    /**
+     * The type of document being used as address verification.
+     * [Required]
+     * Enum: "proof_of_address"
+     *
+     * @var string value of ProofOfPrincipalAddressType
+     */
+    public $type;
+
+    /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
+     */
+    public $front;
+}
diff --git a/lib/Checkout/Accounts/ProofOfPrincipalAddressType.php b/lib/Checkout/Accounts/ProofOfPrincipalAddressType.php
new file mode 100644
index 0000000..e2c25d9
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfPrincipalAddressType.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * The document type accepted as proof of the company's principal place of business when
+ * onboarding a sub-entity (company variants, Accounts API v3.0).
+ *
+ * Carries the same proof_of_address value as ProofOfResidentialAddressType, but the spec defines
+ * the two as separate enums on separate documents; see that class.
+ */
+class ProofOfPrincipalAddressType
+{
+    public static $proof_of_address = "proof_of_address";
+}
diff --git a/lib/Checkout/Accounts/ProofOfRegistration.php b/lib/Checkout/Accounts/ProofOfRegistration.php
new file mode 100644
index 0000000..9d4156b
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfRegistration.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * Proof of the sole trader's registration, for example an extract from a trade register.
+ *
+ * Belongs on company.representatives[].documents (see RepresentativeDocuments), never on the
+ * top-level request documents. Required for the EEA Sole Trader - Full (3.0) variant.
+ */
+class ProofOfRegistration
+{
+    /**
+     * The type of document being used as proof of registration.
+     * [Required]
+     * Enum: "extract_from_trade_register", "other"
+     *
+     * @var string value of ProofOfRegistrationType
+     */
+    public $type;
+
+    /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
+     */
+    public $front;
+}
diff --git a/lib/Checkout/Accounts/ProofOfRegistrationType.php b/lib/Checkout/Accounts/ProofOfRegistrationType.php
new file mode 100644
index 0000000..b6de63e
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfRegistrationType.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * The document types accepted as a sole trader's proof of registration when onboarding a
+ * sub-entity (EEA Sole Trader, Accounts API v3.0).
+ */
+class ProofOfRegistrationType
+{
+    public static $extract_from_trade_register = "extract_from_trade_register";
+    public static $other = "other";
+}
diff --git a/lib/Checkout/Accounts/ProofOfResidentialAddress.php b/lib/Checkout/Accounts/ProofOfResidentialAddress.php
new file mode 100644
index 0000000..4c1af9f
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfResidentialAddress.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * Proof of residential address of the representative.
+ *
+ * Belongs on company.representatives[].documents (see RepresentativeDocuments), never on the
+ * top-level request documents. Required for the EEA Sole Trader - Full (3.0) variant.
+ */
+class ProofOfResidentialAddress
+{
+    /**
+     * The type of document being used as address verification.
+     * [Required]
+     * Enum: "proof_of_address"
+     *
+     * @var string value of ProofOfResidentialAddressType
+     */
+    public $type;
+
+    /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
+     */
+    public $front;
+}
diff --git a/lib/Checkout/Accounts/ProofOfResidentialAddressType.php b/lib/Checkout/Accounts/ProofOfResidentialAddressType.php
new file mode 100644
index 0000000..b380a08
--- /dev/null
+++ b/lib/Checkout/Accounts/ProofOfResidentialAddressType.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * The document type accepted as a representative's proof of residential address when onboarding
+ * a sub-entity (EEA Sole Trader, Accounts API v3.0).
+ *
+ * Carries the same proof_of_address value as ProofOfPrincipalAddressType, but the spec defines
+ * the two as separate enums on separate documents: this one on the representative, that one on
+ * the company. They are kept apart on purpose so a change to one does not silently change the
+ * other.
+ */
+class ProofOfResidentialAddressType
+{
+    public static $proof_of_address = "proof_of_address";
+}
diff --git a/lib/Checkout/Accounts/Representative.php b/lib/Checkout/Accounts/Representative.php
index 04f071d..c269e59 100644
--- a/lib/Checkout/Accounts/Representative.php
+++ b/lib/Checkout/Accounts/Representative.php
@@ -15,6 +15,7 @@ class Representative
     /**
      * The representative's id.
      * [Optional]
+     * ^rep_[a-z0-9]{26}$
      * Length: 30 characters
      *
      * @var string
@@ -59,10 +60,14 @@ class Representative
     public $ownership_percentage;
 
     /**
-     * The representative's verification documents.
-     * [Optional]
+     * The representative's verification documents; see RepresentativeDocuments for which keys
+     * apply to each variant. On the EEA, GB and US Company - Full (3.0) Person of Interest
+     * representatives and the EEA, GB and US Sole Trader - Full (3.0) variants the API rejects any
+     * key it does not recognise. The spec does not declare that restriction for the US ISV Seller
+     * variants (3.0).
+     * [Optional] (required for the sole trader full variants, Accounts API v3.0)
      *
-     * @var OnboardSubEntityDocuments
+     * @var RepresentativeDocuments
      */
     public $documents;
 
diff --git a/lib/Checkout/Accounts/RepresentativeDocuments.php b/lib/Checkout/Accounts/RepresentativeDocuments.php
new file mode 100644
index 0000000..f1a03f3
--- /dev/null
+++ b/lib/Checkout/Accounts/RepresentativeDocuments.php
@@ -0,0 +1,61 @@
+<?php
+
+namespace Checkout\Accounts;
+
+/**
+ * Verification documents for an individual representative, sent as
+ * company.representatives[].documents (Accounts API v3.0).
+ *
+ * Which keys apply depends on the onboarding variant:
+ * - EEA Sole Trader - Full (3.0): identity_verification, proof_of_residential_address and
+ *   proof_of_registration, all three required.
+ * - GB and US Sole Trader - Full (3.0): identity_verification, required.
+ * - EEA, GB and US Company - Full (3.0), Person of Interest representatives:
+ *   identity_verification and certified_authorised_signatory, both optional.
+ * - US ISV Seller Company (3.0): identity_verification and certified_authorised_signatory, both
+ *   optional.
+ * - US ISV Seller Sole Trader (3.0): identity_verification, optional.
+ *
+ * The API validates this object strictly (a key it does not recognise is rejected, not ignored)
+ * only on the EEA, GB and US Company - Full (3.0) Person of Interest representatives and the EEA,
+ * GB and US Sole Trader - Full (3.0) variants. The spec does not declare that restriction for the
+ * US ISV Seller variants (3.0).
+ *
+ * Company-level documents such as bank_verification belong on the top-level request documents
+ * (OnboardSubEntityDocuments), not here.
+ */
+class RepresentativeDocuments
+{
+    /**
+     * The document to use to confirm the individual's identity.
+     * [Optional] (required for the sole trader full variants)
+     *
+     * @var Document
+     */
+    public $identity_verification;
+
+    /**
+     * Certified authorised signatory document. Required when the legal representative or other
+     * role owner is not registered on the certificate of incorporation.
+     * [Optional] (EEA, GB and US Company - Full (3.0) and US ISV Seller Company (3.0) only)
+     *
+     * @var CertifiedAuthorisedSignatory
+     */
+    public $certified_authorised_signatory;
+
+    /**
+     * Proof of residential address of the representative.
+     * [Optional] (required for the EEA Sole Trader - Full (3.0) variant, and only valid there)
+     *
+     * @var ProofOfResidentialAddress
+     */
+    public $proof_of_residential_address;
+
+    /**
+     * Proof of the sole trader's registration, for example an extract from a trade register.
+     * [Optional] (required for the EEA Sole Trader - Full (3.0) variant, and only valid there)
+     *
+     * @var ProofOfRegistration
+     */
+    public $proof_of_registration;
+}
diff --git a/lib/Checkout/Accounts/RepresentativeIndividual.php b/lib/Checkout/Accounts/RepresentativeIndividual.php
index 71cde0a..880aa51 100644
--- a/lib/Checkout/Accounts/RepresentativeIndividual.php
+++ b/lib/Checkout/Accounts/RepresentativeIndividual.php
@@ -56,7 +56,8 @@ class RepresentativeIndividual
 
     /**
      * The list of citizenships or legal statuses for the representative.
-     * [Required] (Accounts API v3.0)
+     * [Required] for the US ISV Seller variants only (Accounts API v3.0). Not part of the other
+     * v3.0 schemas; leave unset for them.
      *
      * @var array values of Citizenship
      */
@@ -64,7 +65,8 @@ class RepresentativeIndividual
 
     /**
      * The classification of the national identification number provided.
-     * [Required] (Accounts API v3.0)
+     * [Required] for the US ISV Seller variants only (Accounts API v3.0). Not part of the other
+     * v3.0 schemas; leave unset for them.
      * Enum: "ssn", "itin", "passport", "driving_license", "national_id_card", "residence_permit", "other"
      *
      * @var string value of NationalIdType
@@ -73,16 +75,20 @@ class RepresentativeIndividual
 
     /**
      * The representative's national identification number.
-     * [Optional]
-     * Format: region-specific (validated by the API against the sub-entity's country)
+     * [Required] for the US ISV Seller variants; [Optional] for the other v3.0 variants.
+     * The format depends on the variant:
+     * - US ISV Seller: the number for the national_id_type given. ^[a-zA-Z0-9\-]+$,
+     *   Length: 5 to 16 characters.
+     * - Other v3.0 variants: a Social Security Number (SSN) or Individual Taxpayer Identification
+     *   Number (ITIN), US residents only. ^\d{9}$, Length: 9 characters.
      *
      * @var string
      */
     public $national_id_number;
 
     /**
-     * The representative's email address.
-     * [Optional]
+     * The representative's personal email address.
+     * [Required] for the US ISV Seller variants; [Optional] for the other v3.0 variants.
      * Format: email
      *
      * @var string
@@ -91,7 +97,7 @@ class RepresentativeIndividual
 
     /**
      * The representative's phone number.
-     * [Optional]
+     * [Required] for the US ISV Seller variants; [Optional] for the other v3.0 variants.
      *
      * @var Phone
      */
diff --git a/lib/Checkout/Accounts/ShareholderStructure.php b/lib/Checkout/Accounts/ShareholderStructure.php
index c58a099..06886f6 100644
--- a/lib/Checkout/Accounts/ShareholderStructure.php
+++ b/lib/Checkout/Accounts/ShareholderStructure.php
@@ -3,18 +3,27 @@
 namespace Checkout\Accounts;
 
 /**
- * Shareholder structure chart, including the percentage of shares, certified by a competent
- * authority and dated within the last 3 months.
+ * Shareholder structure chart (including % of shares) certified by a competent authority
+ * individual and dated within the last 3 months.
  */
 class ShareholderStructure
 {
     /**
+     * The type of document.
+     * [Required]
+     * Enum: "certified_shareholder_structure"
+     *
      * @var string value of ShareholderStructureType
      */
     public $type;
 
     /**
-     * @var string the ID of the front side of the document, as returned when the file was uploaded
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
+     * @var string
      */
     public $front;
 }
diff --git a/lib/Checkout/Accounts/TaxVerification.php b/lib/Checkout/Accounts/TaxVerification.php
index 24bb20b..4d8b29c 100644
--- a/lib/Checkout/Accounts/TaxVerification.php
+++ b/lib/Checkout/Accounts/TaxVerification.php
@@ -2,14 +2,27 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * IRS-issued Employer Identification Number document used to verify the entity's tax
+ * identification (US variants).
+ */
 class TaxVerification
 {
     /**
+     * The type of IRS-issued document used for tax verification.
+     * [Required]
+     * Enum: "ein_letter"
+     *
      * @var string value of TaxVerificationType
      */
     public $type;
 
     /**
+     * The ID of the front side of the document as represented within Checkout.com systems.
+     * [Required]
+     * ^file_[a-z2-7]{26}$
+     * Length: 31 characters
+     *
      * @var string
      */
     public $front;
diff --git a/lib/Checkout/Accounts/TaxVerificationType.php b/lib/Checkout/Accounts/TaxVerificationType.php
index 3e07595..9526f7e 100644
--- a/lib/Checkout/Accounts/TaxVerificationType.php
+++ b/lib/Checkout/Accounts/TaxVerificationType.php
@@ -2,6 +2,10 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * The document type accepted as tax verification when onboarding a sub-entity (US Company and
+ * US ISV Seller variants): an IRS-issued Employer Identification Number letter.
+ */
 class TaxVerificationType
 {
     public static $ein_letter = "ein_letter";
diff --git a/lib/Checkout/Accounts/UpdatePaymentInstrumentRequest.php b/lib/Checkout/Accounts/UpdatePaymentInstrumentRequest.php
index 20e1d28..c19552f 100644
--- a/lib/Checkout/Accounts/UpdatePaymentInstrumentRequest.php
+++ b/lib/Checkout/Accounts/UpdatePaymentInstrumentRequest.php
@@ -2,19 +2,36 @@
 
 namespace Checkout\Accounts;
 
+/**
+ * Request for PATCH /accounts/entities/{entityId}/payment-instruments/{id}
+ * (PlatformsPaymentInstrumentUpdate).
+ */
 class UpdatePaymentInstrumentRequest
 {
     /**
+     * A reference that you can use to identify the payment instrument.
+     * [Optional]
+     * min 1 character, max 50 characters
+     *
      * @var string
      */
     public $label;
 
     /**
+     * Deprecated by the API: for scheduled payouts the first payment instrument created for a
+     * currency is used; to change it, update the payout schedule.
+     * [Optional]
+     *
      * @var bool
      */
     public $default;
 
     /**
+     * The payment instrument ETag, as returned in the ETag header of the GET, in $headers->if_match.
+     * AccountsClient::updateBankPaymentInstrumentDetails sends it as the If-Match HTTP header; the
+     * API answers 428 without it and 412 when it does not match.
+     * [Required] by the API.
+     *
      * @var Headers
      */
     public $headers;
diff --git a/test/Checkout/Tests/Accounts/AccountsClientEntityRequirementsTest.php b/test/Checkout/Tests/Accounts/AccountsClientEntityRequirementsTest.php
index 6a3c56f..2d96159 100644
--- a/test/Checkout/Tests/Accounts/AccountsClientEntityRequirementsTest.php
+++ b/test/Checkout/Tests/Accounts/AccountsClientEntityRequirementsTest.php
@@ -37,8 +37,8 @@ public function shouldGetEntityRequirements()
             ->willReturn([
                 "data" => [
                     [
-                        "id" => "req_123",
-                        "resource" => "ent_456",
+                        "id" => "req_5wmacwhrhbzhqkhx5hlqmzje44",
+                        "resource" => "ent_azsiyswl7bwe2ynjzujy7lcjca",
                         "reason" => "periodic_review",
                         "priority" => "high"
                     ]
@@ -58,8 +58,8 @@ public function shouldGetEntityRequirementDetails()
         $this->apiClient
             ->method("get")
             ->willReturn([
-                "id" => "req_123",
-                "resource" => "ent_456",
+                "id" => "req_5wmacwhrhbzhqkhx5hlqmzje44",
+                "resource" => "ent_azsiyswl7bwe2ynjzujy7lcjca",
                 "reason" => "periodic_review",
                 "priority" => "high",
                 "message" => "Please provide your ID",
@@ -79,13 +79,13 @@ public function shouldResolveEntityRequirement()
         $this->apiClient
             ->method("put")
             ->willReturn([
-                "id" => "req_123",
+                "id" => "req_5wmacwhrhbzhqkhx5hlqmzje44",
                 "status" => "processing",
                 "submitted_at" => "2026-05-05T10:15:30Z"
             ]);
 
         $request = new EntityRequirementUpdateRequest();
-        $request->value = ["file_id" => "file_test123"];
+        $request->value = ["file_id" => "file_awonj5x3g4oupitqp6dhsc4hyy"];
         
         $response = $this->client->resolveEntityRequirement("entity_id", "requirement_id", $request);
         $this->assertNotNull($response);
@@ -100,7 +100,7 @@ public function shouldResolveEntityRequirementWithStringValue()
         $this->apiClient
             ->method("put")
             ->willReturn([
-                "id" => "req_123",
+                "id" => "req_5wmacwhrhbzhqkhx5hlqmzje44",
                 "status" => "processing",
                 "submitted_at" => "2026-05-05T10:15:30Z"
             ]);
diff --git a/test/Checkout/Tests/Accounts/AccountsClientTest.php b/test/Checkout/Tests/Accounts/AccountsClientTest.php
index 7bd584f..0e95d85 100644
--- a/test/Checkout/Tests/Accounts/AccountsClientTest.php
+++ b/test/Checkout/Tests/Accounts/AccountsClientTest.php
@@ -8,6 +8,7 @@
 use Checkout\Accounts\OnboardEntityRequest;
 use Checkout\Accounts\PaymentInstrumentRequest;
 use Checkout\Accounts\PaymentInstrumentsQuery;
+use Checkout\Accounts\Headers;
 use Checkout\Accounts\UpdatePaymentInstrumentRequest;
 use Checkout\Accounts\UpdateScheduleRequest;
 use Checkout\Accounts\ReserveRules\Requests\CreateReserveRuleRequest;
@@ -220,6 +221,33 @@ public function shouldUpdateBankPaymentInstrument()
         $this->assertNotNull($response);
     }
 
+    /**
+     * @test
+     * @throws CheckoutApiException
+     */
+    public function shouldSendUpdateBankPaymentInstrumentEtagAsIfMatchHeader()
+    {
+        $request = new UpdatePaymentInstrumentRequest();
+        $request->label = "Renamed account";
+        $request->headers = new Headers();
+        $request->headers->if_match = '"Y3Y9MCZydj0w"';
+
+        $this->apiClient
+            ->expects($this->once())
+            ->method("patch")
+            ->with(
+                "accounts/entities/entity_id/payment-instruments/instrument_id",
+                $request,
+                $this->anything(),
+                $this->identicalTo($request->headers)
+            )
+            ->willReturn(["response"]);
+
+        $response = $this->client->updateBankPaymentInstrumentDetails("entity_id", "instrument_id", $request);
+
+        $this->assertNotNull($response);
+    }
+
     /**
      * @test
      * @throws CheckoutApiException
@@ -228,7 +256,7 @@ public function shouldGetSubEntityMembers()
     {
         $this->apiClient
             ->method("get")
-            ->willReturn(["data" => [["user_id" => "usr_test123"]]]);
+            ->willReturn(["data" => [["user_id" => "usr_eyk754cqieqexfh6u46no5nnha"]]]);
 
         $response = $this->client->getSubEntityMembers("entity_id");
 
@@ -244,7 +272,7 @@ public function shouldReinviteSubEntityMember()
     {
         $this->apiClient
             ->method("put")
-            ->willReturn(["id" => "usr_test123"]);
+            ->willReturn(["id" => "usr_eyk754cqieqexfh6u46no5nnha"]);
 
         $response = $this->client->reinviteSubEntityMember("entity_id", "user_id");
 
@@ -260,7 +288,10 @@ public function shouldCreateReserveRule()
     {
         $this->apiClient
             ->method("post")
-            ->willReturn(["id" => "rsv_test123", "_links" => ["self" => ["href" => "/reserve-rules/rsv_test123"]]]);
+            ->willReturn([
+                "id" => "rsv_qn4nis4k3ykpzzu7cvtuvhqqga",
+                "_links" => ["self" => ["href" => "/reserve-rules/rsv_qn4nis4k3ykpzzu7cvtuvhqqga"]]
+            ]);
 
         $request = $this->buildCreateReserveRuleRequest();
         $response = $this->client->createReserveRule("entity_id", $request);
@@ -277,7 +308,7 @@ public function shouldGetReserveRules()
     {
         $this->apiClient
             ->method("get")
-            ->willReturn(["data" => [["id" => "rsv_test123", "type" => "rolling"]]]);
+            ->willReturn(["data" => [["id" => "rsv_qn4nis4k3ykpzzu7cvtuvhqqga", "type" => "rolling"]]]);
 
         $response = $this->client->getReserveRules("entity_id");
 
@@ -293,7 +324,11 @@ public function shouldGetReserveRuleDetails()
     {
         $this->apiClient
             ->method("get")
-            ->willReturn(["id" => "rsv_test123", "type" => "rolling", "valid_from" => "2024-01-01T00:00:00Z"]);
+            ->willReturn([
+                "id" => "rsv_qn4nis4k3ykpzzu7cvtuvhqqga",
+                "type" => "rolling",
+                "valid_from" => "2024-01-01T00:00:00Z"
+            ]);
 
         $response = $this->client->getReserveRuleDetails("entity_id", "reserve_rule_id");
 
@@ -310,7 +345,10 @@ public function shouldUpdateReserveRule()
     {
         $this->apiClient
             ->method("put")
-            ->willReturn(["id" => "rsv_test123", "_links" => ["self" => ["href" => "/reserve-rules/rsv_test123"]]]);
+            ->willReturn([
+                "id" => "rsv_qn4nis4k3ykpzzu7cvtuvhqqga",
+                "_links" => ["self" => ["href" => "/reserve-rules/rsv_qn4nis4k3ykpzzu7cvtuvhqqga"]]
+            ]);
 
         $request = $this->buildUpdateReserveRuleRequest();
         $response = $this->client->updateReserveRule("entity_id", "reserve_rule_id", "etag_value", $request);
@@ -325,31 +363,44 @@ public function shouldUpdateReserveRule()
      */
     public function shouldUploadFile()
     {
+        // Per-field examples of PlatformsFileUploadResponse in the spec.
+        $expected = [
+            "id" => "file_6lbss42ezvoufcb2beo76rvwly",
+            "maximum_size_in_bytes" => 4194304,
+            "document_types_for_purpose" => ["image/jpeg", "image/png", "image/jpg"],
+            "_links" => [
+                "upload" => [
+                    "href" => "https://s3.eu-west-1.amazonaws.com/mp-files-api-staging-prod/"
+                        . "ent_ociwguf5a5fe3ndmpnvpnwsi3e/file_6lbss42ezvoufcb2beo76rvwly"
+                        . "?AWSAccessKeyId=ASIX4BFJOBCQFLAMPKU3&Expires=1661355993&x-amz-security-token=some_token"
+                ],
+                "self" => [
+                    "href" => "https://files.checkout.com/files/file_6lbss42ezvoufcb2beo76rvwly"
+                ]
+            ]
+        ];
+
         $this->apiClient
             ->method("post")
-            ->willReturn([
-                "id" => "file_6lbss42ezvoufcb2beo76rvwly",
-                "maximum_size_in_bytes" => 4194304,
-                "document_types_for_purpose" => ["image/jpeg", "image/png", "image/jpg"],
-                "_links" => [
-                    "upload" => [
-                        "href" => "https://s3.eu-west-1.amazonaws.com/mp-files-api-staging-prod/ent_ociwguf5a5fe3ndmpnvpnwsi3e/file_6lbss42ezvoufcb2beo76rvwly?AWSAccessKeyId=ASIX4BFJOBCQFLAMPKU3&Expires=1661355993&x-amz-security-token=some_token"
-                    ],
-                    "self" => [
-                        "href" => "https://files.checkout.com/files/file_6lbss42ezvoufcb2beo76rvwly"
-                    ]
-                ]
-            ]);
+            ->willReturn($expected);
 
         $fileRequest = $this->buildUploadFileRequest();
         $response = $this->client->uploadFile("entity_id", $fileRequest);
 
-        $this->assertNotNull($response);
-        $this->assertArrayHasKey("id", $response);
-        $this->assertArrayHasKey("maximum_size_in_bytes", $response);
-        $this->assertArrayHasKey("document_types_for_purpose", $response);
-        $this->assertArrayHasKey("_links", $response);
-        $this->assertEquals("file_6lbss42ezvoufcb2beo76rvwly", $response["id"]);
+        $this->assertSame("file_6lbss42ezvoufcb2beo76rvwly", $response["id"]);
+        $this->assertSame(4194304, $response["maximum_size_in_bytes"]);
+        $this->assertSame(["image/jpeg", "image/png", "image/jpg"], $response["document_types_for_purpose"]);
+        $this->assertSame(
+            "https://s3.eu-west-1.amazonaws.com/mp-files-api-staging-prod/"
+            . "ent_ociwguf5a5fe3ndmpnvpnwsi3e/file_6lbss42ezvoufcb2beo76rvwly"
+            . "?AWSAccessKeyId=ASIX4BFJOBCQFLAMPKU3&Expires=1661355993&x-amz-security-token=some_token",
+            $response["_links"]["upload"]["href"]
+        );
+        $this->assertSame(
+            "https://files.checkout.com/files/file_6lbss42ezvoufcb2beo76rvwly",
+            $response["_links"]["self"]["href"]
+        );
+        $this->assertSame($expected, $response);
     }
 
     /**
@@ -358,38 +409,52 @@ public function shouldUploadFile()
      */
     public function shouldRetrieveFile()
     {
+        // Per-field examples of PlatformsFileRetrieveResponse in the spec, including the
+        // seven fractional digits of uploaded_on, which the SDK returns as an unparsed string.
+        $expected = [
+            "id" => "file_6lbss42ezvoufcb2beo76rvwly",
+            "status" => "invalid",
+            "status_reasons" => ["InvalidMimeType"],
+            "size" => 1024,
+            "mime_type" => "application/pdf",
+            "uploaded_on" => "2020-12-01T15:01:01.0000000+00:00",
+            "purpose" => "identity_verification",
+            "_links" => [
+                "download" => [
+                    "href" => "https://s3.eu-west-1.amazonaws.com/mp-files-api-clean-prod/"
+                        . "ent_ociwguf5a5fe3ndmpnvpnwsi3e/file_6lbss42ezvoufcb2beo76rvwly"
+                        . "?X-Amz-Expires=3600&x-amz-security-token=some_token"
+                ],
+                "self" => [
+                    "href" => "https://files.checkout.com/files/file_6lbss42ezvoufcb2beo76rvwly"
+                ]
+            ]
+        ];
+
         $this->apiClient
             ->method("get")
-            ->willReturn([
-                "id" => "file_6lbss42ezvoufcb2beo76rvwly",
-                "status" => "valid",
-                "status_reasons" => null,
-                "size" => 1024,
-                "mime_type" => "application/pdf",
-                "uploaded_on" => "2020-12-01T15:01:01Z",
-                "purpose" => "identity_verification",
-                "_links" => [
-                    "download" => [
-                        "href" => "https://s3.eu-west-1.amazonaws.com/mp-files-api-clean-prod/ent_ociwguf5a5fe3ndmpnvpnwsi3e/file_6lbss42ezvoufcb2beo76rvwly?X-Amz-Expires=3600&x-amz-security-token=some_token"
-                    ],
-                    "self" => [
-                        "href" => "https://files.checkout.com/files/file_6lbss42ezvoufcb2beo76rvwly"
-                    ]
-                ]
-            ]);
+            ->willReturn($expected);
 
         $response = $this->client->retrieveFile("entity_id", "file_6lbss42ezvoufcb2beo76rvwly");
 
-        $this->assertNotNull($response);
-        $this->assertArrayHasKey("id", $response);
-        $this->assertArrayHasKey("status", $response);
-        $this->assertArrayHasKey("size", $response);
-        $this->assertArrayHasKey("mime_type", $response);
-        $this->assertArrayHasKey("uploaded_on", $response);
-        $this->assertArrayHasKey("purpose", $response);
-        $this->assertArrayHasKey("_links", $response);
-        $this->assertEquals("file_6lbss42ezvoufcb2beo76rvwly", $response["id"]);
-        $this->assertEquals("valid", $response["status"]);
+        $this->assertSame("file_6lbss42ezvoufcb2beo76rvwly", $response["id"]);
+        $this->assertSame("invalid", $response["status"]);
+        $this->assertSame(["InvalidMimeType"], $response["status_reasons"]);
+        $this->assertSame(1024, $response["size"]);
+        $this->assertSame("application/pdf", $response["mime_type"]);
+        $this->assertSame("2020-12-01T15:01:01.0000000+00:00", $response["uploaded_on"]);
+        $this->assertSame("identity_verification", $response["purpose"]);
+        $this->assertSame(
+            "https://s3.eu-west-1.amazonaws.com/mp-files-api-clean-prod/"
+            . "ent_ociwguf5a5fe3ndmpnvpnwsi3e/file_6lbss42ezvoufcb2beo76rvwly"
+            . "?X-Amz-Expires=3600&x-amz-security-token=some_token",
+            $response["_links"]["download"]["href"]
+        );
+        $this->assertSame(
+            "https://files.checkout.com/files/file_6lbss42ezvoufcb2beo76rvwly",
+            $response["_links"]["self"]["href"]
+        );
+        $this->assertSame($expected, $response);
     }
 
     /**
diff --git a/test/Checkout/Tests/Accounts/AccountsIntegrationTest.php b/test/Checkout/Tests/Accounts/AccountsIntegrationTest.php
index 155f0e0..9842b3b 100644
--- a/test/Checkout/Tests/Accounts/AccountsIntegrationTest.php
+++ b/test/Checkout/Tests/Accounts/AccountsIntegrationTest.php
@@ -4,10 +4,13 @@
 
 use Checkout\Accounts\AccountsFileRequest;
 use Checkout\Accounts\BusinessType;
+use Checkout\Accounts\CertifiedAuthorisedSignatory;
+use Checkout\Accounts\CertifiedAuthorisedSignatoryType;
 use Checkout\Accounts\Company;
 use Checkout\Accounts\ContactDetails;
 use Checkout\Accounts\DateOfBirth;
 use Checkout\Accounts\DateOfIncorporation;
+use Checkout\Accounts\Document;
 use Checkout\Accounts\EntityEmailAddresses;
 use Checkout\Accounts\EntityRoles;
 use Checkout\Accounts\InstrumentDetailsFasterPayments;
@@ -18,14 +21,20 @@
 use Checkout\Accounts\ProcessingDetailsAch;
 use Checkout\Accounts\ProcessingDetailsPayments;
 use Checkout\Accounts\PaymentInstrumentRequest;
+use Checkout\Accounts\Headers;
+use Checkout\Accounts\UpdatePaymentInstrumentRequest;
+use Checkout\Accounts\InstrumentAccountType;
+use Checkout\Accounts\InstrumentDetailsAch;
 use Checkout\Accounts\PaymentInstrumentsQuery;
 use Checkout\Accounts\Profile;
 use Checkout\Accounts\Representative;
+use Checkout\Accounts\RepresentativeDocuments;
 use Checkout\Accounts\RepresentativeIndividual;
 use Checkout\Accounts\ReserveRules\Requests\CreateReserveRuleRequest;
 use Checkout\Accounts\ReserveRules\Requests\UpdateReserveRuleRequest;
 use Checkout\Accounts\ReserveRules\Entities\Rolling;
 use Checkout\Accounts\ReserveRules\Entities\HoldingDuration;
+use Checkout\Accounts\Files\Entities\FilePurpose;
 use Checkout\Accounts\Files\Requests\UploadFileRequest;
 use Checkout\CheckoutApi;
 use Checkout\CheckoutApiException;
@@ -34,6 +43,7 @@
 use Checkout\CheckoutSdk;
 use Checkout\Common\Country;
 use Checkout\Common\Currency;
+use Checkout\Common\DocumentType;
 use Checkout\Common\InstrumentType;
 use Checkout\Common\Phone;
 use Checkout\OAuthScope;
@@ -93,6 +103,79 @@ public function shouldCreateGetAndUpdateOnboardEntity()
         $this->assertEquals($response["id"], $updateResponse["id"]);
     }
 
+    /**
+     * The representative's documents go through RepresentativeDocuments. The sandbox platform
+     * resolves to a company variant, where identity_verification and certified_authorised_signatory
+     * are the representative documents the API accepts.
+     *
+     * @test
+     * @throws CheckoutApiException
+     */
+    public function shouldCreateEntityWithRepresentativeDocuments()
+    {
+        $identityFile = $this->uploadFile(FilePurpose::$identity_verification);
+        $signatoryFile = $this->uploadFile(FilePurpose::$certified_authorised_signatory);
+
+        $identity = new Document();
+        $identity->type = DocumentType::$passport;
+        $identity->front = $identityFile["id"];
+
+        $signatory = new CertifiedAuthorisedSignatory();
+        $signatory->type = CertifiedAuthorisedSignatoryType::$power_of_attorney;
+        $signatory->front = $signatoryFile["id"];
+
+        $documents = new RepresentativeDocuments();
+        $documents->identity_verification = $identity;
+        $documents->certified_authorised_signatory = $signatory;
+
+        $onboardEntityRequest = $this->buildOnboardCompanyRequest();
+        $onboardEntityRequest->company->representatives[0]->documents = $documents;
+
+        $response = $this->accountsApi()->getAccountsClient()->createEntity($onboardEntityRequest);
+
+        $this->assertResponse($response, "id", "reference");
+
+        // The documents are linked on the representative, not dropped: the API echoes them back.
+        $entity = $this->accountsApi()->getAccountsClient()->getEntity($response["id"]);
+        $this->assertResponse($entity, "company.representatives");
+        $linked = $entity["company"]["representatives"][0]["documents"];
+        $this->assertEquals(
+            array("type" => DocumentType::$passport, "front" => $identityFile["id"]),
+            $linked["identity_verification"]
+        );
+        $this->assertEquals(
+            array("type" => CertifiedAuthorisedSignatoryType::$power_of_attorney, "front" => $signatoryFile["id"]),
+            $linked["certified_authorised_signatory"]
+        );
+    }
+
+    /**
+     * The two EEA Sole Trader representative documents need their own upload purposes before
+     * they can be linked on the representative. Goes through POST /entities/{id}/files, the
+     * endpoint whose request schema (PlatformsFileUpload) defines the purpose enum.
+     *
+     * @test
+     * @throws CheckoutApiException
+     */
+    public function shouldUploadRepresentativeProofFiles()
+    {
+        $entityId = $this->createTestEntity();
+        $purposes = array(FilePurpose::$proof_of_residential_address, FilePurpose::$proof_of_registration);
+
+        foreach ($purposes as $purpose) {
+            $uploadRequest = new UploadFileRequest();
+            $uploadRequest->purpose = $purpose;
+
+            $uploadResponse = $this->accountsApi()->getAccountsClient()->uploadFile($entityId, $uploadRequest);
+            $this->validateFileUploadResponse($uploadResponse);
+
+            $retrieveResponse = $this->accountsApi()->getAccountsClient()
+                ->retrieveFile($entityId, $uploadResponse["id"]);
+            $this->validateFileRetrieveResponse($retrieveResponse);
+            $this->assertEquals($purpose, $retrieveResponse["purpose"]);
+        }
+    }
+
     /**
      * @test
      * @throws CheckoutApiException
@@ -144,6 +227,50 @@ public function shouldCreateAndRetrievePaymentInstrument()
         $this->assertResponse($queryResponse, "data");
     }
 
+    /**
+     * The update only succeeds when the ETag reaches the API as the If-Match HTTP header: without it
+     * the API answers 428, and with a stale ETag 412.
+     *
+     * @test
+     * @throws CheckoutApiException
+     * @throws CheckoutArgumentException
+     * @throws CheckoutException
+     */
+    public function shouldUpdatePaymentInstrumentWithEtag()
+    {
+        $client = $this->accountsApi()->getAccountsClient();
+        $entity = $client->createEntity($this->buildOnboardCompanyRequest());
+        $file = $this->uploadFile();
+
+        $instrumentRequest = new PaymentInstrumentRequest();
+        $instrumentRequest->label = "Main account";
+        $instrumentRequest->type = InstrumentType::$bank_account;
+        $instrumentRequest->currency = Currency::$USD;
+        $instrumentRequest->country = Country::$US;
+        $instrumentRequest->document = new InstrumentDocument();
+        $instrumentRequest->document->type = "bank_statement";
+        $instrumentRequest->document->file_id = $file["id"];
+        $instrumentRequest->instrument_details = new InstrumentDetailsAch();
+        $instrumentRequest->instrument_details->account_number = "123456789";
+        $instrumentRequest->instrument_details->routing_number = "026009593";
+        // The sandbox rejects checking (instrument_details_account_type_invalid), although the spec lists it.
+        $instrumentRequest->instrument_details->account_type = InstrumentAccountType::$savings;
+        $instrumentId = $client->createBankPaymentInstrument($entity["id"], $instrumentRequest)["id"];
+
+        $details = $client->retrievePaymentInstrumentDetails($entity["id"], $instrumentId);
+        $responseHeaders = array_change_key_case($details["http_metadata"]->getHeaders(), CASE_LOWER);
+
+        $updateRequest = new UpdatePaymentInstrumentRequest();
+        $updateRequest->label = "Renamed account";
+        $updateRequest->headers = new Headers();
+        $updateRequest->headers->if_match = $responseHeaders["etag"][0];
+        $response = $client->updateBankPaymentInstrumentDetails($entity["id"], $instrumentId, $updateRequest);
+
+        $this->assertEquals($instrumentId, $response["id"]);
+        $updated = $client->retrievePaymentInstrumentDetails($entity["id"], $instrumentId);
+        $this->assertEquals("Renamed account", $updated["label"]);
+    }
+
     /**
      * @test
      * @throws CheckoutApiException
@@ -295,7 +422,6 @@ public function shouldUpdateReserveRule()
 
     /**
      * @test
-     * @skip API temporarily unavailable
      * @throws CheckoutApiException
      */
     public function shouldUploadAndRetrieveFile()
@@ -611,15 +737,16 @@ private function getAccountsCheckoutApi()
     }
 
     /**
+     * @param string $purpose value of FilePurpose
      * @return array
      * @throws CheckoutApiException
      */
-    public function uploadFile()
+    public function uploadFile($purpose = "bank_verification")
     {
         $fileRequest = new AccountsFileRequest();
         $fileRequest->file = $this->getCheckoutFilePath();
         $fileRequest->content_type = "image/jpeg";
-        $fileRequest->purpose = "bank_verification";
+        $fileRequest->purpose = $purpose;
 
         $response = $this->accountsApi()->getAccountsClient()->submitFile($fileRequest);
 
diff --git a/test/Checkout/Tests/Accounts/AccountsSchemaVersionHeaderTest.php b/test/Checkout/Tests/Accounts/AccountsSchemaVersionHeaderTest.php
index ed8e789..a062b00 100644
--- a/test/Checkout/Tests/Accounts/AccountsSchemaVersionHeaderTest.php
+++ b/test/Checkout/Tests/Accounts/AccountsSchemaVersionHeaderTest.php
@@ -3,9 +3,23 @@
 namespace Checkout\Tests\Accounts;
 
 use Checkout\Accounts\AccountsClient;
+use Checkout\Accounts\BankVerification;
+use Checkout\Accounts\BankVerificationType;
+use Checkout\Accounts\BusinessType;
+use Checkout\Accounts\Company;
+use Checkout\Accounts\Document;
+use Checkout\Accounts\EntityRoles;
 use Checkout\Accounts\OnboardEntityRequest;
+use Checkout\Accounts\OnboardSubEntityDocuments;
+use Checkout\Accounts\ProofOfRegistration;
+use Checkout\Accounts\ProofOfRegistrationType;
+use Checkout\Accounts\ProofOfResidentialAddress;
+use Checkout\Accounts\ProofOfResidentialAddressType;
+use Checkout\Accounts\Representative;
+use Checkout\Accounts\RepresentativeDocuments;
 use Checkout\ApiClient;
 use Checkout\CheckoutConfiguration;
+use Checkout\Common\DocumentType;
 use Checkout\Environment;
 use Checkout\HttpClientBuilderInterface;
 use Checkout\PlatformType;
@@ -42,7 +56,7 @@ private function createCapturingHttpClient(): \GuzzleHttp\Client
 
         $stack->setHandler(function () {
             return \GuzzleHttp\Promise\Create::promiseFor(
-                new Response(200, ['Content-Type' => 'application/json'], '{"id":"ent_123"}')
+                new Response(200, ['Content-Type' => 'application/json'], '{"id":"ent_w4jelhppmfiufdnatam37wrfc4"}')
             );
         });
 
@@ -100,7 +114,7 @@ public function createEntitySendsSchemaVersion3ByDefault()
      */
     public function getEntitySendsSchemaVersion3ByDefault()
     {
-        $this->buildAccountsClient()->getEntity('ent_123');
+        $this->buildAccountsClient()->getEntity('ent_w4jelhppmfiufdnatam37wrfc4');
         $this->assertAcceptHeader('application/json;schema_version=3.0');
     }
 
@@ -109,7 +123,7 @@ public function getEntitySendsSchemaVersion3ByDefault()
      */
     public function updateEntitySendsSchemaVersion3ByDefault()
     {
-        $this->buildAccountsClient()->updateEntity('ent_123', new OnboardEntityRequest());
+        $this->buildAccountsClient()->updateEntity('ent_w4jelhppmfiufdnatam37wrfc4', new OnboardEntityRequest());
         $this->assertAcceptHeader('application/json;schema_version=3.0');
     }
 
@@ -118,7 +132,7 @@ public function updateEntitySendsSchemaVersion3ByDefault()
      */
     public function getEntityRequirementsSendsSchemaVersion3ByDefault()
     {
-        $this->buildAccountsClient()->getEntityRequirements('ent_123');
+        $this->buildAccountsClient()->getEntityRequirements('ent_w4jelhppmfiufdnatam37wrfc4');
         $this->assertAcceptHeader('application/json;schema_version=3.0');
     }
 
@@ -127,7 +141,85 @@ public function getEntityRequirementsSendsSchemaVersion3ByDefault()
      */
     public function allowsOverridingTheSchemaVersion()
     {
-        $this->buildAccountsClient()->getEntity('ent_123', '2.0');
+        $this->buildAccountsClient()->getEntity('ent_w4jelhppmfiufdnatam37wrfc4', '2.0');
         $this->assertAcceptHeader('application/json;schema_version=2.0');
     }
+
+    /**
+     * The EEA Sole Trader (3.0) representative documents cannot be exercised against the sandbox,
+     * whose platform is not EEA-scoped, so this asserts the bytes that reach the wire instead: on
+     * POST and PUT, the three documents sit under company.representatives[0].documents, on the v3.0
+     * schema, and only bank_verification is sent at the top level.
+     *
+     * @test
+     */
+    public function eeaSoleTraderRepresentativeDocumentsReachTheWire()
+    {
+        $expectedRepresentativeDocuments = array(
+            "identity_verification" => array("type" => "passport", "front" => "file_identityverificationaaaaaa"),
+            "proof_of_residential_address" => array(
+                "type" => "proof_of_address",
+                "front" => "file_proofofresidentialaddressa",
+            ),
+            "proof_of_registration" => array(
+                "type" => "extract_from_trade_register",
+                "front" => "file_proofofregistrationaaaaaaa",
+            ),
+        );
+
+        $this->buildAccountsClient()->createEntity($this->buildEeaSoleTraderRequest());
+        $this->assertSame('POST', $this->capturedRequest->getMethod());
+        $this->assertSame('/accounts/entities', $this->capturedRequest->getUri()->getPath());
+        $this->assertAcceptHeader('application/json;schema_version=3.0');
+        $body = json_decode((string) $this->capturedRequest->getBody(), true);
+        $this->assertSame($expectedRepresentativeDocuments, $body['company']['representatives'][0]['documents']);
+        $this->assertSame(array('bank_verification'), array_keys($body['documents']));
+
+        $this->buildAccountsClient()->updateEntity(
+            'ent_w4jelhppmfiufdnatam37wrfc4',
+            $this->buildEeaSoleTraderRequest()
+        );
+        $this->assertSame('PUT', $this->capturedRequest->getMethod());
+        $this->assertSame(
+            '/accounts/entities/ent_w4jelhppmfiufdnatam37wrfc4',
+            $this->capturedRequest->getUri()->getPath()
+        );
+        $body = json_decode((string) $this->capturedRequest->getBody(), true);
+        $this->assertSame($expectedRepresentativeDocuments, $body['company']['representatives'][0]['documents']);
+    }
+
+    private function buildEeaSoleTraderRequest(): OnboardEntityRequest
+    {
+        $identity = new Document();
+        $identity->type = DocumentType::$passport;
+        $identity->front = "file_identityverificationaaaaaa";
+
+        $proofOfResidentialAddress = new ProofOfResidentialAddress();
+        $proofOfResidentialAddress->type = ProofOfResidentialAddressType::$proof_of_address;
+        $proofOfResidentialAddress->front = "file_proofofresidentialaddressa";
+
+        $proofOfRegistration = new ProofOfRegistration();
+        $proofOfRegistration->type = ProofOfRegistrationType::$extract_from_trade_register;
+        $proofOfRegistration->front = "file_proofofregistrationaaaaaaa";
+
+        $representative = new Representative();
+        $representative->roles = array(EntityRoles::$ubo);
+        $representative->documents = new RepresentativeDocuments();
+        $representative->documents->identity_verification = $identity;
+        $representative->documents->proof_of_residential_address = $proofOfResidentialAddress;
+        $representative->documents->proof_of_registration = $proofOfRegistration;
+
+        $bankVerification = new BankVerification();
+        $bankVerification->type = BankVerificationType::$bank_statement;
+        $bankVerification->front = "file_bankverificationaaaaaaaaaa";
+
+        $request = new OnboardEntityRequest();
+        $request->reference = "ref_sole_trader";
+        $request->company = new Company();
+        $request->company->business_type = BusinessType::$individual_or_sole_proprietorship;
+        $request->company->representatives = array($representative);
+        $request->documents = new OnboardSubEntityDocuments();
+        $request->documents->bank_verification = $bankVerification;
+        return $request;
+    }
 }
diff --git a/test/Checkout/Tests/Accounts/CompanySerializationTest.php b/test/Checkout/Tests/Accounts/CompanySerializationTest.php
index e9dffdf..1b5cad9 100644
--- a/test/Checkout/Tests/Accounts/CompanySerializationTest.php
+++ b/test/Checkout/Tests/Accounts/CompanySerializationTest.php
@@ -7,12 +7,14 @@
 use Checkout\Accounts\CompanyPosition;
 use Checkout\Accounts\DateOfBirth;
 use Checkout\Accounts\DateOfIncorporation;
+use Checkout\Accounts\EntityFinancialDetails;
 use Checkout\Accounts\EntityRoles;
 use Checkout\Accounts\PlaceOfBirth;
 use Checkout\Accounts\Representative;
 use Checkout\Accounts\RepresentativeIndividual;
 use Checkout\Common\Address;
 use Checkout\Common\Country;
+use Checkout\Common\Currency;
 use Checkout\JsonSerializer;
 use PHPUnit\Framework\TestCase;
 
@@ -31,9 +33,12 @@ public function testCompanyWithV3RepresentativeRoundTrip()
         $company->legal_name = "Super Hero Masks Inc.";
         $company->trading_name = "Super Hero Masks";
         $company->additional_trading_names = array("SHM");
-        $company->is_registered_company = true;
+        // The spec enum is [false] only: the flag exists to declare an unregistered company.
+        $company->is_registered_company = false;
         $company->regulatory_licence_number = "REG-123456";
         $company->date_of_incorporation = $dateOfIncorporation;
+        $company->principal_address = $this->buildAddress("1 Principal Street", "W1T 4TJ");
+        $company->registered_address = $this->buildAddress("2 Registered Street", "EC1A 1BB");
         $company->representatives = array($this->buildRepresentative());
 
         $decoded = json_decode((new JsonSerializer())->serialize($company), true);
@@ -43,9 +48,29 @@ public function testCompanyWithV3RepresentativeRoundTrip()
         $this->assertSame("Super Hero Masks Inc.", $decoded['legal_name']);
         $this->assertSame("Super Hero Masks", $decoded['trading_name']);
         $this->assertSame(array("SHM"), $decoded['additional_trading_names']);
-        $this->assertTrue($decoded['is_registered_company']);
+        // false must be sent, not dropped like null.
+        $this->assertArrayHasKey('is_registered_company', $decoded);
+        $this->assertFalse($decoded['is_registered_company']);
         $this->assertSame("REG-123456", $decoded['regulatory_licence_number']);
-        $this->assertSame(2010, $decoded['date_of_incorporation']['year']);
+        $this->assertSame(array("day" => 1, "month" => 6, "year" => 2010), $decoded['date_of_incorporation']);
+        $this->assertSame(
+            array(
+                "address_line1" => "1 Principal Street",
+                "city" => "London",
+                "zip" => "W1T 4TJ",
+                "country" => "GB",
+            ),
+            $decoded['principal_address']
+        );
+        $this->assertSame(
+            array(
+                "address_line1" => "2 Registered Street",
+                "city" => "London",
+                "zip" => "EC1A 1BB",
+                "country" => "GB",
+            ),
+            $decoded['registered_address']
+        );
 
         $representative = $decoded['representatives'][0];
         $this->assertSame("John", $representative['individual']['first_name']);
@@ -58,6 +83,35 @@ public function testCompanyWithV3RepresentativeRoundTrip()
         );
     }
 
+    /**
+     * company.financial_details exists in the EEA and US Company (2.0) variants, with these four
+     * fields.
+     */
+    public function testCompanyV2FinancialDetailsRoundTrip()
+    {
+        $financialDetails = new EntityFinancialDetails();
+        $financialDetails->annual_processing_volume = 120000;
+        $financialDetails->average_transaction_value = 500;
+        $financialDetails->highest_transaction_value = 2500;
+        $financialDetails->currency = Currency::$USD;
+
+        $company = new Company();
+        $company->legal_name = "Super Hero Masks Inc.";
+        $company->financial_details = $financialDetails;
+
+        $decoded = json_decode((new JsonSerializer())->serialize($company), true);
+
+        $this->assertSame(
+            array(
+                "annual_processing_volume" => 120000,
+                "average_transaction_value" => 500,
+                "highest_transaction_value" => 2500,
+                "currency" => "USD",
+            ),
+            $decoded['financial_details']
+        );
+    }
+
     public function testRolesSerializeToExactSwaggerValues()
     {
         $this->assertSame("ubo", EntityRoles::$ubo);
@@ -70,21 +124,51 @@ public function testRolesSerializeToExactSwaggerValues()
     public function testBusinessTypeValuesMatchSwagger()
     {
         $this->assertSame("individual_or_sole_proprietorship", BusinessType::$individual_or_sole_proprietorship);
+        $this->assertSame("general_partnership", BusinessType::$general_partnership);
+        $this->assertSame("limited_partnership", BusinessType::$limited_partnership);
+        $this->assertSame("scottish_limited_partnership", BusinessType::$scottish_limited_partnership);
+        $this->assertSame("public_limited_company", BusinessType::$public_limited_company);
+        $this->assertSame("limited_company", BusinessType::$limited_company);
         $this->assertSame("limited_liability_corporation", BusinessType::$limited_liability_corporation);
+        $this->assertSame("private_corporation", BusinessType::$private_corporation);
+        $this->assertSame("publicly_traded_corporation", BusinessType::$publicly_traded_corporation);
+        $this->assertSame("professional_association", BusinessType::$professional_association);
+        $this->assertSame("unincorporated_association", BusinessType::$unincorporated_association);
+        $this->assertSame("auto_entrepreneur", BusinessType::$auto_entrepreneur);
         $this->assertSame("government_agency", BusinessType::$government_agency);
         $this->assertSame("non_profit_entity", BusinessType::$non_profit_entity);
         $this->assertSame("trust", BusinessType::$trust);
-        $this->assertSame("scottish_limited_partnership", BusinessType::$scottish_limited_partnership);
+        $this->assertSame("club_or_society", BusinessType::$club_or_society);
+        $this->assertSame("regulated_financial_institution", BusinessType::$regulated_financial_institution);
+        $this->assertSame("cftc_registered_entity", BusinessType::$cftc_registered_entity);
+        $this->assertSame("sec_registered_entity", BusinessType::$sec_registered_entity);
     }
 
     public function testCompanyPositionValuesMatchSwagger()
     {
         $this->assertSame("ceo", CompanyPosition::$ceo);
+        $this->assertSame("cfo", CompanyPosition::$cfo);
+        $this->assertSame("coo", CompanyPosition::$coo);
         $this->assertSame("managing_member", CompanyPosition::$managing_member);
         $this->assertSame("general_partner", CompanyPosition::$general_partner);
+        $this->assertSame("president", CompanyPosition::$president);
+        $this->assertSame("vice_president", CompanyPosition::$vice_president);
+        $this->assertSame("treasurer", CompanyPosition::$treasurer);
+        $this->assertSame("other_senior_management", CompanyPosition::$other_senior_management);
+        $this->assertSame("other_executive_officer", CompanyPosition::$other_executive_officer);
         $this->assertSame("other_non_executive_non_senior", CompanyPosition::$other_non_executive_non_senior);
     }
 
+    private function buildAddress($line1, $zip)
+    {
+        $address = new Address();
+        $address->address_line1 = $line1;
+        $address->city = "London";
+        $address->zip = $zip;
+        $address->country = Country::$GB;
+        return $address;
+    }
+
     private function buildRepresentative()
     {
         $dateOfBirth = new DateOfBirth();
diff --git a/test/Checkout/Tests/Accounts/ContactDetailsSerializationTest.php b/test/Checkout/Tests/Accounts/ContactDetailsSerializationTest.php
new file mode 100644
index 0000000..8b7c8fa
--- /dev/null
+++ b/test/Checkout/Tests/Accounts/ContactDetailsSerializationTest.php
@@ -0,0 +1,99 @@
+<?php
+
+namespace Checkout\Tests\Accounts;
+
+use Checkout\Accounts\ContactDetails;
+use Checkout\Accounts\EntityEmailAddresses;
+use Checkout\Accounts\Invitee;
+use Checkout\Common\Phone;
+use Checkout\JsonSerializer;
+use PHPUnit\Framework\TestCase;
+
+class ContactDetailsSerializationTest extends TestCase
+{
+    public function testContactDetailsInviteeRoundTrip()
+    {
+        $phone = new Phone();
+        $phone->country_code = "FR";
+        $phone->number = "0712345678";
+
+        $emailAddresses = new EntityEmailAddresses();
+        $emailAddresses->primary = "owner@example.com";
+
+        $invitee = new Invitee();
+        $invitee->email = "invitee@example.com";
+
+        $contactDetails = new ContactDetails();
+        $contactDetails->phone = $phone;
+        $contactDetails->email_addresses = $emailAddresses;
+        $contactDetails->invitee = $invitee;
+
+        $decoded = json_decode((new JsonSerializer())->serialize($contactDetails), true);
+
+        $this->assertSame(
+            array(
+                "phone" => array("country_code" => "FR", "number" => "0712345678"),
+                "email_addresses" => array("primary" => "owner@example.com"),
+                "invitee" => array("email" => "invitee@example.com"),
+            ),
+            $decoded
+        );
+    }
+
+    public function testUsIsvSellerContactDetailsMatchSwaggerExample()
+    {
+        // contact_details from the US ISV Seller Company (3.0) request example in the spec, with a
+        // neutral primary address in place of the example's.
+        $swaggerExample = '{"phone":{"country_code":"US","number":"4155678900"},'
+            . '"email_addresses":{"primary":"owner@example.com",'
+            . '"pci_compliance_contact":"pci.contact@example.com"}}';
+
+        $phone = new Phone();
+        $phone->country_code = "US";
+        $phone->number = "4155678900";
+
+        $emailAddresses = new EntityEmailAddresses();
+        $emailAddresses->primary = "owner@example.com";
+        $emailAddresses->pci_compliance_contact = "pci.contact@example.com";
+
+        $contactDetails = new ContactDetails();
+        $contactDetails->phone = $phone;
+        $contactDetails->email_addresses = $emailAddresses;
+
+        $serialized = (new JsonSerializer())->serialize($contactDetails);
+        $decoded = json_decode($serialized, true);
+
+        $this->assertSame("owner@example.com", $decoded["email_addresses"]["primary"]);
+        $this->assertSame("pci.contact@example.com", $decoded["email_addresses"]["pci_compliance_contact"]);
+        $this->assertArrayNotHasKey("invitee", $decoded);
+        $this->assertEquals(json_decode($swaggerExample, true), $decoded);
+    }
+
+    /**
+     * In every v2.0 variant contact_details.phone defines number only; country_code exists only
+     * in v3.0. Leaving country_code unset must drop the key, not send it as null.
+     */
+    public function testV2NumberOnlyPhoneOmitsCountryCode()
+    {
+        $phone = new Phone();
+        $phone->number = "4155678900";
+
+        $emailAddresses = new EntityEmailAddresses();
+        $emailAddresses->primary = "owner@example.com";
+
+        $contactDetails = new ContactDetails();
+        $contactDetails->phone = $phone;
+        $contactDetails->email_addresses = $emailAddresses;
+
+        $decoded = json_decode((new JsonSerializer())->serialize($contactDetails), true);
+
+        $this->assertSame(
+            array(
+                "phone" => array("number" => "4155678900"),
+                "email_addresses" => array("primary" => "owner@example.com"),
+            ),
+            $decoded
+        );
+        $this->assertArrayNotHasKey("country_code", $decoded["phone"]);
+    }
+}
diff --git a/test/Checkout/Tests/Accounts/IndividualSerializationTest.php b/test/Checkout/Tests/Accounts/IndividualSerializationTest.php
new file mode 100644
index 0000000..1bcc323
--- /dev/null
+++ b/test/Checkout/Tests/Accounts/IndividualSerializationTest.php
@@ -0,0 +1,74 @@
+<?php
+
+namespace Checkout\Tests\Accounts;
+
+use Checkout\Accounts\DateOfBirth;
+use Checkout\Accounts\Identification;
+use Checkout\Accounts\Individual;
+use Checkout\Accounts\PlaceOfBirth;
+use Checkout\Common\Address;
+use Checkout\Common\Country;
+use Checkout\JsonSerializer;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * The top-level individual of the Sole Trader (2.0) variants. place_of_birth is defined by the
+ * EEA variants, identification by the US ones; the model carries both.
+ */
+class IndividualSerializationTest extends TestCase
+{
+    public function testV2IndividualRoundTrip()
+    {
+        $address = new Address();
+        $address->address_line1 = "123 Main Street";
+        $address->address_line2 = "Suite 100";
+        $address->city = "San Francisco";
+        $address->state = "CA";
+        $address->zip = "94105";
+        $address->country = Country::$US;
+
+        $dateOfBirth = new DateOfBirth();
+        $dateOfBirth->day = 15;
+        $dateOfBirth->month = 1;
+        $dateOfBirth->year = 1990;
+
+        $placeOfBirth = new PlaceOfBirth();
+        $placeOfBirth->country = Country::$US;
+
+        $identification = new Identification();
+        $identification->national_id_number = "123456789";
+
+        $individual = new Individual();
+        $individual->first_name = "John";
+        $individual->middle_name = "Robert";
+        $individual->last_name = "Trader";
+        $individual->trading_name = "John's Goods";
+        $individual->registered_address = $address;
+        $individual->date_of_birth = $dateOfBirth;
+        $individual->place_of_birth = $placeOfBirth;
+        $individual->identification = $identification;
+
+        $decoded = json_decode((new JsonSerializer())->serialize($individual), true);
+
+        $this->assertSame(
+            array(
+                "first_name" => "John",
+                "middle_name" => "Robert",
+                "last_name" => "Trader",
+                "trading_name" => "John's Goods",
+                "registered_address" => array(
+                    "address_line1" => "123 Main Street",
+                    "address_line2" => "Suite 100",
+                    "city" => "San Francisco",
+                    "state" => "CA",
+                    "zip" => "94105",
+                    "country" => "US",
+                ),
+                "date_of_birth" => array("day" => 15, "month" => 1, "year" => 1990),
+                "place_of_birth" => array("country" => "US"),
+                "identification" => array("national_id_number" => "123456789"),
+            ),
+            $decoded
+        );
+    }
+}
diff --git a/test/Checkout/Tests/Accounts/OnboardEntityRequestSerializationTest.php b/test/Checkout/Tests/Accounts/OnboardEntityRequestSerializationTest.php
index c8ca95a..24852d2 100644
--- a/test/Checkout/Tests/Accounts/OnboardEntityRequestSerializationTest.php
+++ b/test/Checkout/Tests/Accounts/OnboardEntityRequestSerializationTest.php
@@ -2,25 +2,344 @@
 
 namespace Checkout\Tests\Accounts;
 
+use Checkout\Accounts\AdditionalDocument;
 use Checkout\Accounts\AgreedTerms;
 use Checkout\Accounts\ArticlesOfAssociation;
 use Checkout\Accounts\ArticlesOfAssociationType;
 use Checkout\Accounts\BankVerification;
 use Checkout\Accounts\BankVerificationType;
+use Checkout\Accounts\BusinessType;
+use Checkout\Accounts\Citizenship;
+use Checkout\Accounts\Company;
+use Checkout\Accounts\CompanyPosition;
 use Checkout\Accounts\CompanyVerification;
+use Checkout\Accounts\CompanyVerificationType;
+use Checkout\Accounts\ContactDetails;
+use Checkout\Accounts\DateOfBirth;
+use Checkout\Accounts\DateOfIncorporation;
 use Checkout\Accounts\Document;
+use Checkout\Accounts\EntityEmailAddresses;
+use Checkout\Accounts\EntityRoles;
 use Checkout\Accounts\FinancialStatements;
 use Checkout\Accounts\FinancialStatementsType;
+use Checkout\Accounts\FinancialVerification;
+use Checkout\Accounts\FinancialVerificationType;
+use Checkout\Accounts\NationalIdType;
 use Checkout\Accounts\OnboardEntityRequest;
 use Checkout\Accounts\OnboardSubEntityDocuments;
+use Checkout\Accounts\PlaceOfBirth;
+use Checkout\Accounts\ProcessingDetails;
+use Checkout\Accounts\ProcessingDetailsAch;
+use Checkout\Accounts\ProcessingDetailsPayments;
+use Checkout\Accounts\Profile;
+use Checkout\Accounts\ProofOfLegality;
+use Checkout\Accounts\ProofOfLegalityType;
+use Checkout\Accounts\ProofOfPrincipalAddress;
+use Checkout\Accounts\ProofOfPrincipalAddressType;
+use Checkout\Accounts\Representative;
+use Checkout\Accounts\RepresentativeIndividual;
 use Checkout\Accounts\ShareholderStructure;
 use Checkout\Accounts\ShareholderStructureType;
 use Checkout\Accounts\TaxVerification;
+use Checkout\Accounts\TaxVerificationType;
+use Checkout\Common\Address;
+use Checkout\Common\Country;
+use Checkout\Common\Currency;
+use Checkout\Common\DocumentType;
+use Checkout\Common\Phone;
 use Checkout\JsonSerializer;
 use PHPUnit\Framework\TestCase;
 
 class OnboardEntityRequestSerializationTest extends TestCase
 {
+    // File IDs in the spec format ^file_[a-z2-7]{26}$, keyed by the document field they are sent on.
+    private const FILE_IDS = array(
+        "identity_verification" => "file_identityverificationaaaaaa",
+        "identity_back" => "file_identitybackaaaaaaaaaaaaaa",
+        "company_verification" => "file_companyverificationaaaaaaa",
+        "tax_verification" => "file_taxverificationaaaaaaaaaaa",
+        "articles_of_association" => "file_articlesofassociationaaaaa",
+        "shareholder_structure" => "file_shareholderstructureaaaaaa",
+        "bank_verification" => "file_bankverificationaaaaaaaaaa",
+        "financial_statements" => "file_financialstatementsaaaaaaa",
+        "financial_verification" => "file_financialverificationaaaaa",
+        "proof_of_principal_address" => "file_proofofprincipaladdressaaa",
+        "proof_of_legality" => "file_proofoflegalityaaaaaaaaaaa",
+        "additional_document1" => "file_additionaldocumentoneaaaaa",
+        "additional_document2" => "file_additionaldocumenttwoaaaaa",
+        "additional_document3" => "file_additionaldocumentthreeaaa",
+    );
+
+    /**
+     * The US ISV Seller Company (3.0) and US ISV Seller Sole Trader (3.0) request examples,
+     * verbatim from components.schemas["USISVSellerCompany3-0"].example and
+     * components.schemas["USISVSellerSoleTrader3-0"].example. Kept as raw JSON so a key renamed
+     * in the spec or in the models shows up as a test failure.
+     */
+    private const US_ISV_SELLER_COMPANY_SWAGGER_EXAMPLE = <<<'JSON'
+{
+    "reference": "isv-seller-example001",
+    "agreed_terms": {
+        "date": "2026-07-02T10:30:00.0000000+00:00",
+        "ip_address": "8.8.8.8",
+        "name": "Toby Arden",
+        "email": "toby.arden@example.com",
+        "version": "cko-platform-terms-1.0.0"
+    },
+    "seller_category": "cat_retail_001",
+    "processing_details": {
+        "annual_processing_volume": 1000,
+        "average_transaction_value": 2000,
+        "average_order_fulfillment_time": 3,
+        "target_countries": [
+            "US"
+        ],
+        "currency": "USD",
+        "payments": {
+            "ach": {
+                "annual_ach_volume": 100000,
+                "average_ach_transaction_size": 5000,
+                "estimated_monthly_credit_volume": 50000,
+                "average_credit_amount": 2500
+            }
+        }
+    },
+    "contact_details": {
+        "phone": {
+            "number": "4155678900",
+            "country_code": "US"
+        },
+        "email_addresses": {
+            "primary": "toby.arden@example.com",
+            "pci_compliance_contact": "pci.contact@example.com"
+        }
+    },
+    "profile": {
+        "urls": [
+            "https://www.isv-seller-example.com"
+        ],
+        "mccs": [
+            "5551"
+        ],
+        "holding_currencies": [
+            "USD"
+        ],
+        "default_holding_currency": "USD"
+    },
+    "company": {
+        "business_registration_number": "12-3456789",
+        "business_type": "private_corporation",
+        "legal_name": "ISV Seller Example Inc",
+        "trading_name": "ISV Seller Example",
+        "registered_address": {
+            "address_line1": "123 Main Street",
+            "city": "San Francisco",
+            "state": "CA",
+            "zip": "94105",
+            "country": "US"
+        },
+        "principal_address": {
+            "address_line1": "123 Main Street",
+            "city": "San Francisco",
+            "state": "CA",
+            "zip": "94105",
+            "country": "US"
+        },
+        "date_of_incorporation": {
+            "year": 2025,
+            "month": 10,
+            "day": 1
+        },
+        "representatives": [
+            {
+                "roles": [
+                    "ubo",
+                    "control_person"
+                ],
+                "ownership_percentage": 25,
+                "company_position": "ceo",
+                "individual": {
+                    "first_name": "Toby",
+                    "last_name": "Arden",
+                    "email_address": "toby.arden@example.com",
+                    "national_id_type": "ssn",
+                    "national_id_number": "123456789",
+                    "date_of_birth": {
+                        "day": 15,
+                        "month": 1,
+                        "year": 1990
+                    },
+                    "place_of_birth": {
+                        "country": "US"
+                    },
+                    "citizenships": [
+                        {
+                            "country": "US"
+                        }
+                    ],
+                    "phone": {
+                        "country_code": "US",
+                        "number": "4155678901"
+                    },
+                    "address": {
+                        "address_line1": "123 Main Street",
+                        "city": "San Francisco",
+                        "state": "CA",
+                        "zip": "94105",
+                        "country": "US"
+                    }
+                }
+            },
+            {
+                "roles": [
+                    "authorised_signatory"
+                ],
+                "individual": {
+                    "first_name": "Alex",
+                    "last_name": "Morgan",
+                    "email_address": "alex.morgan@example.com",
+                    "national_id_type": "ssn",
+                    "national_id_number": "987654321",
+                    "date_of_birth": {
+                        "day": 22,
+                        "month": 6,
+                        "year": 1985
+                    },
+                    "place_of_birth": {
+                        "country": "US"
+                    },
+                    "citizenships": [
+                        {
+                            "country": "US"
+                        }
+                    ],
+                    "phone": {
+                        "country_code": "US",
+                        "number": "4155678902"
+                    },
+                    "address": {
+                        "address_line1": "123 Main Street",
+                        "city": "San Francisco",
+                        "state": "CA",
+                        "zip": "94105",
+                        "country": "US"
+                    }
+                }
+            }
+        ]
+    }
+}
+JSON;
+
+    private const US_ISV_SELLER_SOLE_TRADER_SWAGGER_EXAMPLE = <<<'JSON'
+{
+    "reference": "isv-sole-trader-example001",
+    "agreed_terms": {
+        "date": "2026-07-02T10:30:00.0000000+00:00",
+        "ip_address": "8.8.8.8",
+        "name": "Hannah Bret",
+        "email": "hannah.bret@example.com",
+        "version": "cko-platform-terms-1.0.0"
+    },
+    "seller_category": "cat_retail_001",
+    "processing_details": {
+        "annual_processing_volume": 1000,
+        "average_transaction_value": 2000,
+        "average_order_fulfillment_time": 3,
+        "target_countries": [
+            "US"
+        ],
+        "currency": "USD",
+        "payments": {
+            "ach": {
+                "annual_ach_volume": 100000,
+                "average_ach_transaction_size": 5000,
+                "estimated_monthly_credit_volume": 50000,
+                "average_credit_amount": 2500
+            }
+        }
+    },
+    "contact_details": {
+        "phone": {
+            "number": "4155678900",
+            "country_code": "US"
+        },
+        "email_addresses": {
+            "primary": "hannah.bret@example.com",
+            "pci_compliance_contact": "pci.contact@example.com"
+        }
+    },
+    "profile": {
+        "urls": [
+            "https://www.isv-sole-trader-example.com"
+        ],
+        "mccs": [
+            "5551"
+        ],
+        "holding_currencies": [
+            "USD"
+        ],
+        "default_holding_currency": "USD"
+    },
+    "company": {
+        "business_type": "individual_or_sole_proprietorship",
+        "is_registered_company": false,
+        "trading_name": "Hannah's Goods",
+        "date_of_incorporation": {
+            "year": 2025,
+            "month": 10,
+            "day": 1
+        },
+        "principal_address": {
+            "address_line1": "123 Main Street",
+            "city": "San Francisco",
+            "state": "CA",
+            "zip": "94105",
+            "country": "US"
+        },
+        "representatives": [
+            {
+                "roles": [
+                    "ubo"
+                ],
+                "ownership_percentage": 100,
+                "individual": {
+                    "first_name": "Hannah",
+                    "last_name": "Bret",
+                    "email_address": "hannah.bret@example.com",
+                    "national_id_type": "ssn",
+                    "national_id_number": "123456789",
+                    "date_of_birth": {
+                        "day": 15,
+                        "month": 1,
+                        "year": 1990
+                    },
+                    "place_of_birth": {
+                        "country": "US"
+                    },
+                    "citizenships": [
+                        {
+                            "country": "US"
+                        }
+                    ],
+                    "phone": {
+                        "country_code": "US",
+                        "number": "4155678901"
+                    },
+                    "address": {
+                        "address_line1": "123 Main Street",
+                        "city": "San Francisco",
+                        "state": "CA",
+                        "zip": "94105",
+                        "country": "US"
+                    }
+                }
+            }
+        ]
+    }
+}
+JSON;
+
     public function testOnboardEntityRequestRoundTrip()
     {
         $agreedTerms = new AgreedTerms();
@@ -50,34 +369,138 @@ public function testDocumentsRoundTripCoversEveryField()
     {
         $decoded = json_decode((new JsonSerializer())->serialize($this->buildDocuments()), true);
 
-        // Every property of OnboardSubEntityDocuments must serialize with its type + front.
+        // Every typed property of OnboardSubEntityDocuments must serialize with its spec type + front.
         $expectedTypes = array(
-            "identity_verification" => "identity_card",
-            "company_verification" => "certificate_of_incorporation",
-            "tax_verification" => "tax_document",
+            "identity_verification" => "passport",
+            "company_verification" => "incorporation_document",
+            "tax_verification" => "ein_letter",
             "articles_of_association" => "articles_of_association",
             "shareholder_structure" => "certified_shareholder_structure",
             "bank_verification" => "bank_statement",
             "financial_statements" => "financial_statements",
-            "financial_verification" => "financial_verification",
-            "proof_of_principal_address" => "utility_bill",
+            "financial_verification" => "financial_statement",
+            "proof_of_principal_address" => "proof_of_address",
             "proof_of_legality" => "proof_of_legality",
-            "additional_document1" => "additional_document",
-            "additional_document2" => "additional_document",
-            "additional_document3" => "additional_document",
         );
 
         foreach ($expectedTypes as $field => $type) {
             $this->assertArrayHasKey($field, $decoded, "documents.$field must serialize");
             $this->assertSame($type, $decoded[$field]['type'], "documents.$field.type");
-            $this->assertSame("file_$field", $decoded[$field]['front'], "documents.$field.front");
+            $this->assertSame(self::FILE_IDS[$field], $decoded[$field]['front'], "documents.$field.front");
         }
 
-        // identity_verification is a Document (supports back); the others carry type + front only.
-        // articles_of_association, shareholder_structure and bank_verification are their own
-        // classes rather than the generic Document, so this also proves the retyped fields
-        // still serialize to the same JSON.
-        $this->assertSame("back_id", $decoded['identity_verification']['back']);
+        // identity_verification is the only top-level document with a back side.
+        $this->assertSame(self::FILE_IDS["identity_back"], $decoded['identity_verification']['back']);
+        foreach (array_keys($expectedTypes) as $field) {
+            if ($field !== "identity_verification") {
+                $this->assertArrayNotHasKey("back", $decoded[$field], "documents.$field has no back");
+            }
+        }
+
+        // The additional documents carry a file ID only: the API defines no type for them.
+        foreach (array("additional_document1", "additional_document2", "additional_document3") as $field) {
+            $this->assertSame(array("front" => self::FILE_IDS[$field]), $decoded[$field], "documents.$field");
+        }
+    }
+
+    public function testUsIsvSellerCompanyMatchesSwaggerExample()
+    {
+        $dateOfIncorporation = new DateOfIncorporation();
+        $dateOfIncorporation->year = 2025;
+        $dateOfIncorporation->month = 10;
+        $dateOfIncorporation->day = 1;
+
+        $controlPerson = new Representative();
+        $controlPerson->roles = array(EntityRoles::$ubo, EntityRoles::$control_person);
+        $controlPerson->ownership_percentage = 25;
+        $controlPerson->company_position = CompanyPosition::$ceo;
+        $controlPerson->individual = $this->usIsvRepresentativeIndividual(
+            "Toby",
+            "Arden",
+            "toby.arden@example.com",
+            "123456789",
+            $this->dateOfBirth(15, 1, 1990),
+            "4155678901"
+        );
+
+        $signatory = new Representative();
+        $signatory->roles = array(EntityRoles::$authorised_signatory);
+        $signatory->individual = $this->usIsvRepresentativeIndividual(
+            "Alex",
+            "Morgan",
+            "alex.morgan@example.com",
+            "987654321",
+            $this->dateOfBirth(22, 6, 1985),
+            "4155678902"
+        );
+
+        $company = new Company();
+        $company->business_registration_number = "12-3456789";
+        $company->business_type = BusinessType::$private_corporation;
+        $company->legal_name = "ISV Seller Example Inc";
+        $company->trading_name = "ISV Seller Example";
+        $company->registered_address = $this->usIsvAddress();
+        $company->principal_address = $this->usIsvAddress();
+        $company->date_of_incorporation = $dateOfIncorporation;
+        $company->representatives = array($controlPerson, $signatory);
+
+        $request = new OnboardEntityRequest();
+        $request->reference = "isv-seller-example001";
+        $request->agreed_terms = $this->usIsvAgreedTerms("Toby Arden", "toby.arden@example.com");
+        $request->seller_category = "cat_retail_001";
+        $request->processing_details = $this->usIsvProcessingDetails();
+        $request->contact_details = $this->usIsvContactDetails("toby.arden@example.com");
+        $request->profile = $this->usIsvProfile("https://www.isv-seller-example.com");
+        $request->company = $company;
+
+        $this->assertEquals(
+            json_decode(self::US_ISV_SELLER_COMPANY_SWAGGER_EXAMPLE, true),
+            json_decode((new JsonSerializer())->serialize($request), true)
+        );
+    }
+
+    public function testUsIsvSellerSoleTraderMatchesSwaggerExample()
+    {
+        $dateOfIncorporation = new DateOfIncorporation();
+        $dateOfIncorporation->year = 2025;
+        $dateOfIncorporation->month = 10;
+        $dateOfIncorporation->day = 1;
+
+        $owner = new Representative();
+        $owner->roles = array(EntityRoles::$ubo);
+        $owner->ownership_percentage = 100;
+        $owner->individual = $this->usIsvRepresentativeIndividual(
+            "Hannah",
+            "Bret",
+            "hannah.bret@example.com",
+            "123456789",
+            $this->dateOfBirth(15, 1, 1990),
+            "4155678901"
+        );
+
+        $company = new Company();
+        $company->business_type = BusinessType::$individual_or_sole_proprietorship;
+        $company->is_registered_company = false;
+        $company->trading_name = "Hannah's Goods";
+        $company->date_of_incorporation = $dateOfIncorporation;
+        $company->principal_address = $this->usIsvAddress();
+        $company->representatives = array($owner);
+
+        $request = new OnboardEntityRequest();
+        $request->reference = "isv-sole-trader-example001";
+        $request->agreed_terms = $this->usIsvAgreedTerms("Hannah Bret", "hannah.bret@example.com");
+        $request->seller_category = "cat_retail_001";
+        $request->processing_details = $this->usIsvProcessingDetails();
+        $request->contact_details = $this->usIsvContactDetails("hannah.bret@example.com");
+        $request->profile = $this->usIsvProfile("https://www.isv-sole-trader-example.com");
+        $request->company = $company;
+
+        $decoded = json_decode((new JsonSerializer())->serialize($request), true);
+
+        $this->assertEquals(json_decode(self::US_ISV_SELLER_SOLE_TRADER_SWAGGER_EXAMPLE, true), $decoded);
+        // false is a value the API requires here, so it must be sent, not dropped like null.
+        $this->assertArrayHasKey("is_registered_company", $decoded["company"]);
+        $this->assertFalse($decoded["company"]["is_registered_company"]);
     }
 
     private function buildDocuments()
@@ -85,56 +508,172 @@ private function buildDocuments()
         $documents = new OnboardSubEntityDocuments();
 
         $identity = new Document();
-        $identity->type = "identity_card";
-        $identity->front = "file_identity_verification";
-        $identity->back = "back_id";
+        $identity->type = DocumentType::$passport;
+        $identity->front = self::FILE_IDS["identity_verification"];
+        $identity->back = self::FILE_IDS["identity_back"];
         $documents->identity_verification = $identity;
 
         $companyVerification = new CompanyVerification();
-        $companyVerification->type = "certificate_of_incorporation";
-        $companyVerification->front = "file_company_verification";
+        $companyVerification->type = CompanyVerificationType::$incorporation_document;
+        $companyVerification->front = self::FILE_IDS["company_verification"];
         $documents->company_verification = $companyVerification;
 
         $taxVerification = new TaxVerification();
-        $taxVerification->type = "tax_document";
-        $taxVerification->front = "file_tax_verification";
+        $taxVerification->type = TaxVerificationType::$ein_letter;
+        $taxVerification->front = self::FILE_IDS["tax_verification"];
         $documents->tax_verification = $taxVerification;
 
         $articlesOfAssociation = new ArticlesOfAssociation();
         $articlesOfAssociation->type = ArticlesOfAssociationType::$articles_of_association;
-        $articlesOfAssociation->front = "file_articles_of_association";
+        $articlesOfAssociation->front = self::FILE_IDS["articles_of_association"];
         $documents->articles_of_association = $articlesOfAssociation;
 
         $shareholderStructure = new ShareholderStructure();
         $shareholderStructure->type = ShareholderStructureType::$certified_shareholder_structure;
-        $shareholderStructure->front = "file_shareholder_structure";
+        $shareholderStructure->front = self::FILE_IDS["shareholder_structure"];
         $documents->shareholder_structure = $shareholderStructure;
 
         $bankVerification = new BankVerification();
         $bankVerification->type = BankVerificationType::$bank_statement;
-        $bankVerification->front = "file_bank_verification";
+        $bankVerification->front = self::FILE_IDS["bank_verification"];
         $documents->bank_verification = $bankVerification;
 
         $financialStatements = new FinancialStatements();
         $financialStatements->type = FinancialStatementsType::$financial_statements;
-        $financialStatements->front = "file_financial_statements";
+        $financialStatements->front = self::FILE_IDS["financial_statements"];
         $documents->financial_statements = $financialStatements;
 
-        $documents->financial_verification = $this->document("financial_verification", "financial_verification");
-        $documents->proof_of_principal_address = $this->document("proof_of_principal_address", "utility_bill");
-        $documents->proof_of_legality = $this->document("proof_of_legality", "proof_of_legality");
-        $documents->additional_document1 = $this->document("additional_document1", "additional_document");
-        $documents->additional_document2 = $this->document("additional_document2", "additional_document");
-        $documents->additional_document3 = $this->document("additional_document3", "additional_document");
+        $financialVerification = new FinancialVerification();
+        $financialVerification->type = FinancialVerificationType::$financial_statement;
+        $financialVerification->front = self::FILE_IDS["financial_verification"];
+        $documents->financial_verification = $financialVerification;
+
+        $proofOfPrincipalAddress = new ProofOfPrincipalAddress();
+        $proofOfPrincipalAddress->type = ProofOfPrincipalAddressType::$proof_of_address;
+        $proofOfPrincipalAddress->front = self::FILE_IDS["proof_of_principal_address"];
+        $documents->proof_of_principal_address = $proofOfPrincipalAddress;
+
+        $proofOfLegality = new ProofOfLegality();
+        $proofOfLegality->type = ProofOfLegalityType::$proof_of_legality;
+        $proofOfLegality->front = self::FILE_IDS["proof_of_legality"];
+        $documents->proof_of_legality = $proofOfLegality;
+
+        $documents->additional_document1 = $this->additionalDocument(self::FILE_IDS["additional_document1"]);
+        $documents->additional_document2 = $this->additionalDocument(self::FILE_IDS["additional_document2"]);
+        $documents->additional_document3 = $this->additionalDocument(self::FILE_IDS["additional_document3"]);
 
         return $documents;
     }
 
-    private function document($field, $type)
+    private function additionalDocument($front)
     {
-        $document = new Document();
-        $document->type = $type;
-        $document->front = "file_$field";
+        $document = new AdditionalDocument();
+        $document->front = $front;
         return $document;
     }
+
+    private function usIsvAddress()
+    {
+        $address = new Address();
+        $address->address_line1 = "123 Main Street";
+        $address->city = "San Francisco";
+        $address->state = "CA";
+        $address->zip = "94105";
+        $address->country = Country::$US;
+        return $address;
+    }
+
+    private function usIsvPhone($number)
+    {
+        $phone = new Phone();
+        $phone->country_code = Country::$US;
+        $phone->number = $number;
+        return $phone;
+    }
+
+    private function dateOfBirth($day, $month, $year)
+    {
+        $dateOfBirth = new DateOfBirth();
+        $dateOfBirth->day = $day;
+        $dateOfBirth->month = $month;
+        $dateOfBirth->year = $year;
+        return $dateOfBirth;
+    }
+
+    private function usIsvRepresentativeIndividual($firstName, $lastName, $email, $ssn, $dateOfBirth, $phoneNumber)
+    {
+        $placeOfBirth = new PlaceOfBirth();
+        $placeOfBirth->country = Country::$US;
+
+        // The spec examples send citizenships[].country only, with no type.
+        $citizenship = new Citizenship();
+        $citizenship->country = Country::$US;
+
+        $individual = new RepresentativeIndividual();
+        $individual->first_name = $firstName;
+        $individual->last_name = $lastName;
+        $individual->email_address = $email;
+        $individual->national_id_type = NationalIdType::$ssn;
+        $individual->national_id_number = $ssn;
+        $individual->date_of_birth = $dateOfBirth;
+        $individual->place_of_birth = $placeOfBirth;
+        $individual->citizenships = array($citizenship);
+        $individual->phone = $this->usIsvPhone($phoneNumber);
+        $individual->address = $this->usIsvAddress();
+        return $individual;
+    }
+
+    private function usIsvAgreedTerms($name, $email)
+    {
+        $agreedTerms = new AgreedTerms();
+        $agreedTerms->date = "2026-07-02T10:30:00.0000000+00:00";
+        $agreedTerms->ip_address = "8.8.8.8";
+        $agreedTerms->name = $name;
+        $agreedTerms->email = $email;
+        $agreedTerms->version = "cko-platform-terms-1.0.0";
+        return $agreedTerms;
+    }
+
+    private function usIsvProcessingDetails()
+    {
+        $ach = new ProcessingDetailsAch();
+        $ach->annual_ach_volume = 100000;
+        $ach->average_ach_transaction_size = 5000;
+        $ach->estimated_monthly_credit_volume = 50000;
+        $ach->average_credit_amount = 2500;
+
+        $payments = new ProcessingDetailsPayments();
+        $payments->ach = $ach;
+
+        $processingDetails = new ProcessingDetails();
+        $processingDetails->annual_processing_volume = 1000;
+        $processingDetails->average_transaction_value = 2000;
+        $processingDetails->average_order_fulfillment_time = 3;
+        $processingDetails->target_countries = array(Country::$US);
+        $processingDetails->currency = Currency::$USD;
+        $processingDetails->payments = $payments;
+        return $processingDetails;
+    }
+
+    private function usIsvContactDetails($primaryEmail)
+    {
+        $emailAddresses = new EntityEmailAddresses();
+        $emailAddresses->primary = $primaryEmail;
+        $emailAddresses->pci_compliance_contact = "pci.contact@example.com";
+
+        $contactDetails = new ContactDetails();
+        $contactDetails->phone = $this->usIsvPhone("4155678900");
+        $contactDetails->email_addresses = $emailAddresses;
+        return $contactDetails;
+    }
+
+    private function usIsvProfile($url)
+    {
+        $profile = new Profile();
+        $profile->urls = array($url);
+        $profile->mccs = array("5551");
+        $profile->holding_currencies = array(Currency::$USD);
+        $profile->default_holding_currency = Currency::$USD;
+        return $profile;
+    }
 }
diff --git a/test/Checkout/Tests/Accounts/OnboardingDocumentTypeTest.php b/test/Checkout/Tests/Accounts/OnboardingDocumentTypeTest.php
index e20d6e4..9500d41 100644
--- a/test/Checkout/Tests/Accounts/OnboardingDocumentTypeTest.php
+++ b/test/Checkout/Tests/Accounts/OnboardingDocumentTypeTest.php
@@ -4,6 +4,14 @@
 
 use Checkout\Accounts\ArticlesOfAssociationType;
 use Checkout\Accounts\BankVerificationType;
+use Checkout\Accounts\CertifiedAuthorisedSignatoryType;
+use Checkout\Accounts\CompanyVerificationType;
+use Checkout\Accounts\FinancialStatementsType;
+use Checkout\Accounts\FinancialVerificationType;
+use Checkout\Accounts\ProofOfLegalityType;
+use Checkout\Accounts\ProofOfPrincipalAddressType;
+use Checkout\Accounts\ProofOfRegistrationType;
+use Checkout\Accounts\ProofOfResidentialAddressType;
 use Checkout\Accounts\ShareholderStructureType;
 use Checkout\Common\DocumentType;
 use PHPUnit\Framework\TestCase;
@@ -27,6 +35,38 @@ public function testExposesTheOnboardingDocumentTypes()
         $this->assertSame("memorandum_of_association", ArticlesOfAssociationType::$memorandum_of_association);
         $this->assertSame("articles_of_association", ArticlesOfAssociationType::$articles_of_association);
         $this->assertSame("certified_shareholder_structure", ShareholderStructureType::$certified_shareholder_structure);
+        $this->assertSame("proof_of_address", ProofOfPrincipalAddressType::$proof_of_address);
+        $this->assertSame("proof_of_legality", ProofOfLegalityType::$proof_of_legality);
+        $this->assertSame("financial_statement", FinancialVerificationType::$financial_statement);
+        $this->assertSame("financial_statements", FinancialStatementsType::$financial_statements);
+        $this->assertSame("incorporation_document", CompanyVerificationType::$incorporation_document);
+        $this->assertSame("articles_of_association", CompanyVerificationType::$articles_of_association);
+    }
+
+    /**
+     * The identity_verification document types, the same six values in every variant.
+     */
+    public function testExposesTheIdentityDocumentTypes()
+    {
+        $this->assertSame("passport", DocumentType::$passport);
+        $this->assertSame("national_identity_card", DocumentType::$national_identity_card);
+        $this->assertSame("driving_license", DocumentType::$driving_license);
+        $this->assertSame("citizen_card", DocumentType::$citizen_card);
+        $this->assertSame("residence_permit", DocumentType::$residence_permit);
+        $this->assertSame("electoral_id", DocumentType::$electoral_id);
+    }
+
+    /**
+     * The document types of the representative documents (company.representatives[].documents).
+     * proof_of_address appears on both ProofOfResidentialAddressType and ProofOfPrincipalAddressType
+     * on purpose: the spec defines them as two enums on two different documents.
+     */
+    public function testExposesTheRepresentativeDocumentTypes()
+    {
+        $this->assertSame("proof_of_address", ProofOfResidentialAddressType::$proof_of_address);
+        $this->assertSame("extract_from_trade_register", ProofOfRegistrationType::$extract_from_trade_register);
+        $this->assertSame("other", ProofOfRegistrationType::$other);
+        $this->assertSame("power_of_attorney", CertifiedAuthorisedSignatoryType::$power_of_attorney);
     }
 
     /**
@@ -48,5 +88,8 @@ public function testKeepsOnboardingTypesOutOfTheIdentityDocumentType()
         $this->assertNotContains("bank_statement", $identity);
         $this->assertNotContains("articles_of_association", $identity);
         $this->assertNotContains("certified_shareholder_structure", $identity);
+        $this->assertNotContains("proof_of_address", $identity);
+        $this->assertNotContains("extract_from_trade_register", $identity);
+        $this->assertNotContains("power_of_attorney", $identity);
     }
 }
diff --git a/test/Checkout/Tests/Accounts/RepresentativeDocumentsSerializationTest.php b/test/Checkout/Tests/Accounts/RepresentativeDocumentsSerializationTest.php
new file mode 100644
index 0000000..451dc46
--- /dev/null
+++ b/test/Checkout/Tests/Accounts/RepresentativeDocumentsSerializationTest.php
@@ -0,0 +1,202 @@
+<?php
+
+namespace Checkout\Tests\Accounts;
+
+use Checkout\Accounts\BankVerification;
+use Checkout\Accounts\BankVerificationType;
+use Checkout\Accounts\BusinessType;
+use Checkout\Accounts\CertifiedAuthorisedSignatory;
+use Checkout\Accounts\CertifiedAuthorisedSignatoryType;
+use Checkout\Accounts\Company;
+use Checkout\Accounts\Document;
+use Checkout\Accounts\EntityRoles;
+use Checkout\Accounts\OnboardEntityRequest;
+use Checkout\Accounts\OnboardSubEntityDocuments;
+use Checkout\Accounts\ProofOfRegistration;
+use Checkout\Accounts\ProofOfRegistrationType;
+use Checkout\Accounts\ProofOfResidentialAddress;
+use Checkout\Accounts\ProofOfResidentialAddressType;
+use Checkout\Accounts\Representative;
+use Checkout\Accounts\RepresentativeDocuments;
+use Checkout\Accounts\RepresentativeIndividual;
+use Checkout\Common\DocumentType;
+use Checkout\JsonSerializer;
+use PHPUnit\Framework\TestCase;
+use ReflectionClass;
+use ReflectionProperty;
+
+class RepresentativeDocumentsSerializationTest extends TestCase
+{
+    /**
+     * Regression: EEA Sole Trader (3.0) needs proof_of_residential_address and proof_of_registration
+     * on company.representatives[].documents. Neither was expressible on the representative model;
+     * both existed only as upload purposes. Reported internally.
+     */
+    public function testEeaSoleTraderRepresentativeDocuments()
+    {
+        $representative = new Representative();
+        $representative->individual = $this->buildIndividual();
+        $representative->roles = array(EntityRoles::$ubo);
+        $representative->documents = $this->buildEeaSoleTraderDocuments();
+
+        $company = new Company();
+        $company->trading_name = "Test Sole Trader";
+        $company->business_type = BusinessType::$individual_or_sole_proprietorship;
+        $company->representatives = array($representative);
+
+        $bankVerification = new BankVerification();
+        $bankVerification->type = BankVerificationType::$bank_statement;
+        $bankVerification->front = "file_bankverificationaaaaaaaaaa";
+
+        $request = new OnboardEntityRequest();
+        $request->reference = "ref_sole_trader";
+        $request->company = $company;
+        $request->documents = new OnboardSubEntityDocuments();
+        $request->documents->bank_verification = $bankVerification;
+
+        $body = (new JsonSerializer())->serialize($request);
+        $decoded = json_decode($body, true);
+
+        $this->assertSame(
+            array(
+                "identity_verification" => array(
+                    "type" => "passport",
+                    "front" => "file_identityverificationaaaaaa",
+                ),
+                "proof_of_residential_address" => array(
+                    "type" => "proof_of_address",
+                    "front" => "file_proofofresidentialaddressa",
+                ),
+                "proof_of_registration" => array(
+                    "type" => "extract_from_trade_register",
+                    "front" => "file_proofofregistrationaaaaaaa",
+                ),
+            ),
+            $decoded['company']['representatives'][0]['documents']
+        );
+
+        // The representative documents stay on the representative; the top level carries only
+        // bank_verification.
+        $this->assertSame(
+            array("bank_verification" => array(
+                "type" => "bank_statement",
+                "front" => "file_bankverificationaaaaaaaaaa",
+            )),
+            $decoded['documents']
+        );
+
+        // Key-level check on the raw body, so a naming change cannot pass silently.
+        $this->assertStringContainsString('"proof_of_residential_address":{', $body);
+        $this->assertStringContainsString('"proof_of_registration":{', $body);
+    }
+
+    public function testCertifiedAuthorisedSignatoryOnCompanyRepresentative()
+    {
+        $signatory = new CertifiedAuthorisedSignatory();
+        $signatory->type = CertifiedAuthorisedSignatoryType::$power_of_attorney;
+        $signatory->front = "file_signatoryaaaaaaaaaaaaaaaaa";
+
+        $documents = new RepresentativeDocuments();
+        $documents->certified_authorised_signatory = $signatory;
+
+        $representative = new Representative();
+        $representative->roles = array(EntityRoles::$legal_representative);
+        $representative->documents = $documents;
+
+        $decoded = json_decode((new JsonSerializer())->serialize($representative), true);
+
+        $this->assertSame(
+            array("certified_authorised_signatory" => array(
+                "type" => "power_of_attorney",
+                "front" => "file_signatoryaaaaaaaaaaaaaaaaa",
+            )),
+            $decoded['documents']
+        );
+    }
+
+    /**
+     * These four are the only keys company.representatives[].documents defines in any v3.0
+     * variant. The EEA, GB and US Company - Full (3.0) Person of Interest representatives and the
+     * EEA, GB and US Sole Trader - Full (3.0) variants reject any other key
+     * (additionalProperties: false), so a property added here by mistake would fail those requests.
+     */
+    public function testRepresentativeDocumentsDeclaresOnlyTheKeysTheApiAccepts()
+    {
+        $properties = array_map(
+            function (ReflectionProperty $property) {
+                return $property->getName();
+            },
+            (new ReflectionClass(RepresentativeDocuments::class))->getProperties()
+        );
+
+        $this->assertSame(
+            array(
+                "identity_verification",
+                "certified_authorised_signatory",
+                "proof_of_residential_address",
+                "proof_of_registration",
+            ),
+            $properties
+        );
+    }
+
+    /**
+     * The typed model is additive: an associative array assigned to Representative::$documents,
+     * as used before RepresentativeDocuments existed, still produces byte-identical JSON.
+     */
+    public function testAssociativeArrayAndTypedModelSerializeIdentically()
+    {
+        $typed = new Representative();
+        $typed->roles = array(EntityRoles::$ubo);
+        $typed->documents = $this->buildEeaSoleTraderDocuments();
+
+        $array = new Representative();
+        $array->roles = array(EntityRoles::$ubo);
+        $array->documents = array(
+            "identity_verification" => array(
+                "type" => "passport",
+                "front" => "file_identityverificationaaaaaa",
+            ),
+            "proof_of_residential_address" => array(
+                "type" => "proof_of_address",
+                "front" => "file_proofofresidentialaddressa",
+            ),
+            "proof_of_registration" => array(
+                "type" => "extract_from_trade_register",
+                "front" => "file_proofofregistrationaaaaaaa",
+            ),
+        );
+
+        $serializer = new JsonSerializer();
+        $this->assertSame($serializer->serialize($array), $serializer->serialize($typed));
+    }
+
+    private function buildEeaSoleTraderDocuments()
+    {
+        $identity = new Document();
+        $identity->type = DocumentType::$passport;
+        $identity->front = "file_identityverificationaaaaaa";
+
+        $proofOfResidentialAddress = new ProofOfResidentialAddress();
+        $proofOfResidentialAddress->type = ProofOfResidentialAddressType::$proof_of_address;
+        $proofOfResidentialAddress->front = "file_proofofresidentialaddressa";
+
+        $proofOfRegistration = new ProofOfRegistration();
+        $proofOfRegistration->type = ProofOfRegistrationType::$extract_from_trade_register;
+        $proofOfRegistration->front = "file_proofofregistrationaaaaaaa";
+
+        $documents = new RepresentativeDocuments();
+        $documents->identity_verification = $identity;
+        $documents->proof_of_residential_address = $proofOfResidentialAddress;
+        $documents->proof_of_registration = $proofOfRegistration;
+        return $documents;
+    }
+
+    private function buildIndividual()
+    {
+        $individual = new RepresentativeIndividual();
+        $individual->first_name = "Jane";
+        $individual->last_name = "Doe";
+        return $individual;
+    }
+}
diff --git a/test/Checkout/Tests/Accounts/RepresentativeIndividualSerializationTest.php b/test/Checkout/Tests/Accounts/RepresentativeIndividualSerializationTest.php
index 01e7b18..9036a8c 100644
--- a/test/Checkout/Tests/Accounts/RepresentativeIndividualSerializationTest.php
+++ b/test/Checkout/Tests/Accounts/RepresentativeIndividualSerializationTest.php
@@ -54,17 +54,37 @@ public function testRepresentativeIndividualRoundTrip()
 
         $decoded = json_decode((new JsonSerializer())->serialize($individual), true);
 
-        $this->assertSame("John", $decoded['first_name']);
-        $this->assertSame("Robert", $decoded['middle_name']);
-        $this->assertSame("Representative", $decoded['last_name']);
-        $this->assertSame("citizenship", $decoded['citizenships'][0]['type']);
-        $this->assertSame("GB", $decoded['citizenships'][0]['country']);
-        $this->assertSame("ssn", $decoded['national_id_type']);
-        $this->assertSame("123456789", $decoded['national_id_number']);
-        $this->assertSame("john@example.com", $decoded['email_address']);
-        $this->assertSame(1996, $decoded['date_of_birth']['year']);
-        $this->assertSame("GB", $decoded['place_of_birth']['country']);
-        $this->assertSame("GB", $decoded['phone']['country_code']);
-        $this->assertSame("W1T 4TJ", $decoded['address']['zip']);
+        $this->assertSame(
+            array(
+                "first_name" => "John",
+                "middle_name" => "Robert",
+                "last_name" => "Representative",
+                "date_of_birth" => array("day" => 5, "month" => 6, "year" => 1996),
+                "place_of_birth" => array("country" => "GB"),
+                "citizenships" => array(array("type" => "citizenship", "country" => "GB")),
+                "national_id_type" => "ssn",
+                "national_id_number" => "123456789",
+                "email_address" => "john@example.com",
+                "phone" => array("country_code" => "GB", "number" => "2072343000"),
+                "address" => array(
+                    "address_line1" => "CheckoutSdk.com",
+                    "city" => "London",
+                    "zip" => "W1T 4TJ",
+                    "country" => "GB",
+                ),
+            ),
+            $decoded
+        );
+    }
+
+    public function testNationalIdTypeValuesMatchSwagger()
+    {
+        $this->assertSame("ssn", NationalIdType::$ssn);
+        $this->assertSame("itin", NationalIdType::$itin);
+        $this->assertSame("passport", NationalIdType::$passport);
+        $this->assertSame("driving_license", NationalIdType::$driving_license);
+        $this->assertSame("national_id_card", NationalIdType::$national_id_card);
+        $this->assertSame("residence_permit", NationalIdType::$residence_permit);
+        $this->assertSame("other", NationalIdType::$other);
     }
 }
diff --git a/test/Checkout/Tests/Accounts/RepresentativeSerializationTest.php b/test/Checkout/Tests/Accounts/RepresentativeSerializationTest.php
new file mode 100644
index 0000000..f59da11
--- /dev/null
+++ b/test/Checkout/Tests/Accounts/RepresentativeSerializationTest.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Checkout\Tests\Accounts;
+
+use Checkout\Accounts\DateOfBirth;
+use Checkout\Accounts\EntityRoles;
+use Checkout\Accounts\Identification;
+use Checkout\Accounts\PlaceOfBirth;
+use Checkout\Accounts\Representative;
+use Checkout\Common\Address;
+use Checkout\Common\Country;
+use Checkout\Common\Phone;
+use Checkout\JsonSerializer;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * company.representatives[] of the Company (2.0) variants: the person fields sit flat on the
+ * representative, and phone is number only.
+ */
+class RepresentativeSerializationTest extends TestCase
+{
+    public function testV2RepresentativeFlatFieldsRoundTrip()
+    {
+        $address = new Address();
+        $address->address_line1 = "123 Main Street";
+        $address->city = "San Francisco";
+        $address->state = "CA";
+        $address->zip = "94105";
+        $address->country = Country::$US;
+
+        $identification = new Identification();
+        $identification->national_id_number = "123456789";
+
+        $phone = new Phone();
+        $phone->number = "4155678901";
+
+        $dateOfBirth = new DateOfBirth();
+        $dateOfBirth->day = 15;
+        $dateOfBirth->month = 1;
+        $dateOfBirth->year = 1990;
+
+        $placeOfBirth = new PlaceOfBirth();
+        $placeOfBirth->country = Country::$US;
+
+        $representative = new Representative();
+        $representative->id = "rep_l2wbgkhgxsoeppr5ffaplhhbh4";
+        $representative->first_name = "John";
+        $representative->last_name = "Representative";
+        $representative->address = $address;
+        $representative->identification = $identification;
+        $representative->phone = $phone;
+        $representative->date_of_birth = $dateOfBirth;
+        $representative->place_of_birth = $placeOfBirth;
+        $representative->roles = array(EntityRoles::$ubo);
+
+        $decoded = json_decode((new JsonSerializer())->serialize($representative), true);
+
+        $this->assertMatchesRegularExpression('/^rep_[a-z0-9]{26}$/', $decoded['id']);
+        $this->assertSame(
+            array(
+                "id" => "rep_l2wbgkhgxsoeppr5ffaplhhbh4",
+                "roles" => array("ubo"),
+                "first_name" => "John",
+                "last_name" => "Representative",
+                "address" => array(
+                    "address_line1" => "123 Main Street",
+                    "city" => "San Francisco",
+                    "state" => "CA",
+                    "zip" => "94105",
+                    "country" => "US",
+                ),
+                "identification" => array("national_id_number" => "123456789"),
+                "phone" => array("number" => "4155678901"),
+                "date_of_birth" => array("day" => 15, "month" => 1, "year" => 1990),
+                "place_of_birth" => array("country" => "US"),
+            ),
+            $decoded
+        );
+    }
+}
diff --git a/test/Checkout/Tests/Accounts/UploadFileRequestSerializationTest.php b/test/Checkout/Tests/Accounts/UploadFileRequestSerializationTest.php
new file mode 100644
index 0000000..24def87
--- /dev/null
+++ b/test/Checkout/Tests/Accounts/UploadFileRequestSerializationTest.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Checkout\Tests\Accounts;
+
+use Checkout\Accounts\Files\Entities\FilePurpose;
+use Checkout\Accounts\Files\Requests\UploadFileRequest;
+use Checkout\JsonSerializer;
+use PHPUnit\Framework\TestCase;
+
+class UploadFileRequestSerializationTest extends TestCase
+{
+    public function testUploadFileRequestSerializesPurpose()
+    {
+        $request = new UploadFileRequest();
+        $request->purpose = FilePurpose::$identity_verification;
+
+        $this->assertSame('{"purpose":"identity_verification"}', (new JsonSerializer())->serialize($request));
+    }
+
+    /**
+     * The 14 values of PlatformsFileUpload.purpose in the spec. The spec schema named FilePurpose
+     * is the disputes enum, not this one.
+     */
+    public function testFilePurposeValuesMatchSwagger()
+    {
+        $this->assertSame("additional_document", FilePurpose::$additional_document);
+        $this->assertSame("articles_of_association", FilePurpose::$articles_of_association);
+        $this->assertSame("bank_verification", FilePurpose::$bank_verification);
+        $this->assertSame("certified_authorised_signatory", FilePurpose::$certified_authorised_signatory);
+        $this->assertSame("company_ownership", FilePurpose::$company_ownership);
+        $this->assertSame("company_verification", FilePurpose::$company_verification);
+        $this->assertSame("financial_verification", FilePurpose::$financial_verification);
+        $this->assertSame("identity_verification", FilePurpose::$identity_verification);
+        $this->assertSame("proof_of_legality", FilePurpose::$proof_of_legality);
+        $this->assertSame("proof_of_principal_address", FilePurpose::$proof_of_principal_address);
+        $this->assertSame("shareholder_structure", FilePurpose::$shareholder_structure);
+        $this->assertSame("tax_verification", FilePurpose::$tax_verification);
+        $this->assertSame("proof_of_residential_address", FilePurpose::$proof_of_residential_address);
+        $this->assertSame("proof_of_registration", FilePurpose::$proof_of_registration);
+    }
+}