diff --git a/src/app/constants.ts b/src/app/constants.ts
index 5320bc977..2d0902528 100644
--- a/src/app/constants.ts
+++ b/src/app/constants.ts
@@ -48,9 +48,12 @@ export const ORCID_URI_REGEXP =
 // https://regex101.com/r/M1fqZi/1
 export const URL_REGEXP =
   /^(?:http(s)?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#%[\]@!\$&'\(\)\*\+\\,;=.>< ]+$/i
-// ISSN pattern using same validation as the backend
-//https://regex101.com/r/NYZTYS/1
-export const ISSN_REGEXP = /\b\d{4}-?\d{3}[\dXx]\b/
+export const ISSN_PORTAL_URL = 'https://portal.issn.org/resource/ISSN/'
+// Escape the URL characters for Regex (handling slashes and dots)
+const escapedUrl = ISSN_PORTAL_URL.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+export const ISSN_REGEXP = new RegExp(`^(?:${escapedUrl})?\\d{4}-?\\d{3}[\\dXx]$`);
+
+
 /* PROTOCOL REQUIRED*/
 // https://regex101.com/r/pSnDC7/1
 export const URL_REGEXP_BACKEND =
@@ -516,3 +519,23 @@ function isValidIsbn13(isbn: string): boolean {
   // The checksum must be perfectly divisible by 10.
   return checksum % 10 === 0
 }
+
+
+function normaliseIssn(issn: string): string {
+    if (issn) {
+      // 1. Remove the portal URL
+      issn = issn.replace(new RegExp(ISSN_PORTAL_URL, 'g'), '')
+
+      // 2. Remove ALL non-alphanumeric characters (spaces, hyphens, dots, etc.)
+      issn = issn.replace(/[^a-zA-Z0-9]/g, '')
+
+      // 3. Force 'X' to uppercase
+      issn = issn.replace(/x/g, 'X')
+
+      // 4. Format as 0000-000X if valid length
+      if (issn.length === 8) {
+        return issn.substring(0, 4) + '-' + issn.substring(4, 8)
+      }
+    }
+    return ''
+  }
\ No newline at end of file
diff --git a/src/app/record/components/affiliation-stacks-groups/modals/modal-affiliations/modal-affiliations.component.ts b/src/app/record/components/affiliation-stacks-groups/modals/modal-affiliations/modal-affiliations.component.ts
index 48d48d04e..e2e7f69ad 100644
--- a/src/app/record/components/affiliation-stacks-groups/modals/modal-affiliations/modal-affiliations.component.ts
+++ b/src/app/record/components/affiliation-stacks-groups/modals/modal-affiliations/modal-affiliations.component.ts
@@ -27,6 +27,7 @@ import { RecordCountriesService } from '../../../../../core/record-countries/rec
 import { first, map, switchMap, tap } from 'rxjs/operators'
 import {
   ISSN_REGEXP,
+  ISSN_PORTAL_URL,
   MAX_LENGTH_LESS_THAN_ONE_THOUSAND,
   MAX_LENGTH_LESS_THAN_TWO_THOUSAND,
   URL_REGEXP,
@@ -63,7 +64,6 @@ export class ModalAffiliationsComponent implements OnInit, OnDestroy {
   issnLabel = $localize`:@@shared.link:Link`
   endDateLabel = $localize`:@@shared.endDate:End date`
 
-  ISSN_PORTAL_URL = 'https://portal.issn.org/resource/ISSN/'
 
   private _type: AffiliationType
   dateLabel: string
@@ -394,13 +394,14 @@ export class ModalAffiliationsComponent implements OnInit, OnDestroy {
       const normalizedIssn = this.normaliseIssn(
         affiliationForm.get('issn')?.value?.trim()
       )
-      const issnUrl = `${this.ISSN_PORTAL_URL}${normalizedIssn}`
+      const issnValue = affiliationForm.get('issn')?.value?.trim();
+      const issnUrl = `${ISSN_PORTAL_URL}${normalizedIssn}`
       affiliationToSave.affiliationExternalIdentifiers = [
         {
           errors: [],
           externalIdentifierId: {
             errors: [],
-            value: affiliationForm.get('issn')?.value?.trim(),
+            value: issnValue && issnValue.startsWith(ISSN_PORTAL_URL)?issnUrl:normalizedIssn,
             required: true,
           },
           externalIdentifierType: { value: 'issn' },
@@ -744,7 +745,7 @@ export class ModalAffiliationsComponent implements OnInit, OnDestroy {
   normaliseIssn(issn: string) {
     if (issn) {
       // 1. Remove the portal URL
-      issn = issn.replace(new RegExp(this.ISSN_PORTAL_URL, 'g'), '')
+      issn = issn.replace(new RegExp(ISSN_PORTAL_URL, 'g'), '')
 
       // 2. Remove ALL non-alphanumeric characters (spaces, hyphens, dots, etc.)
       issn = issn.replace(/[^a-zA-Z0-9]/g, '')
diff --git a/src/app/record/components/work-form/work-form/work-form.component.ts b/src/app/record/components/work-form/work-form/work-form.component.ts
index cad06b7d1..17b84fd92 100644
--- a/src/app/record/components/work-form/work-form/work-form.component.ts
+++ b/src/app/record/components/work-form/work-form/work-form.component.ts
@@ -37,6 +37,7 @@ import {
   MAX_LENGTH_LESS_THAN_TWO_THOUSAND,
   URL_REGEXP,
   isValidISBN,
+  ISSN_REGEXP,
 } from '../../../../constants'
 import {
   Contributor,
@@ -258,6 +259,17 @@ export class WorkFormComponent implements OnInit {
         }
       }
 
+      if (externalIdentifierType === 'issn') {
+        if (!ISSN_REGEXP.test(control.value)) {
+          control.markAsTouched()
+          return of({
+            validFormat: true,
+            resolved: false,
+            attemptedResolution: false,
+          })
+        }
+      }
+
       return this._workService
         .validateWorkIdTypes(externalIdentifierType, control.value)
         .pipe(