diff --git a/apps/edr-passenger-api/src/modules/verifayda/verifayda.dto.ts b/apps/edr-passenger-api/src/modules/verifayda/verifayda.dto.ts
index 26108a452..901118389 100644
--- a/apps/edr-passenger-api/src/modules/verifayda/verifayda.dto.ts
+++ b/apps/edr-passenger-api/src/modules/verifayda/verifayda.dto.ts
@@ -57,6 +57,14 @@ export class CompleteVerificationResultDto {
     agentId?: string;
   };
 
+  @ApiPropertyOptional({
+    description:
+      'eSignet subject identifier for the verified individual (VERIFY flow). A PSUT — ' +
+      'pairwise and stable per client_id, never the FIN. The booking flow compares it across ' +
+      'passengers so one Fayda identity cannot verify more than one passenger on a booking.',
+  })
+  faydaSub?: string;
+
   @ApiPropertyOptional({ description: 'Verified full name from Fayda (VERIFY flow).' })
   fullName?: string;
 
diff --git a/apps/edr-passenger-api/src/modules/verifayda/verifayda.service.ts b/apps/edr-passenger-api/src/modules/verifayda/verifayda.service.ts
index df6cfc21d..42376d4a1 100644
--- a/apps/edr-passenger-api/src/modules/verifayda/verifayda.service.ts
+++ b/apps/edr-passenger-api/src/modules/verifayda/verifayda.service.ts
@@ -70,11 +70,19 @@ export interface FaydaUserSummary {
 /**
  * Result of completing a verification. `verified` is always true on success.
  * LOGIN additionally returns a JWT + user; VERIFY returns the verified identity
- * attributes (name, email, phone, dob, gender) for the caller to consume.
+ * attributes (name, email, phone, dob, gender, faydaSub) for the caller to consume.
  */
 export interface CompleteVerificationResult {
   purpose: VerifaydaPurpose;
   verified: boolean;
+  /**
+   * eSignet subject identifier for the verified individual. This is a PSUT —
+   * pairwise and stable per `client_id`, never the FIN — so it is safe to hand
+   * to the browser, and it is the same value `/passengers/me` already returns.
+   * The booking flow uses it to stop one Fayda identity from verifying more
+   * than one passenger on the same booking.
+   */
+  faydaSub?: string;
   token?: string;
   refreshToken?: string;
   requiresPassword?: boolean;
@@ -280,6 +288,7 @@ export class VerifaydaService {
         result = {
           purpose: 'VERIFY',
           verified: true,
+          faydaSub: normalized.sub,
           fullName: normalized.fullName,
           email: normalized.email,
           phoneNumber: normalized.phoneNumber,
@@ -357,6 +366,13 @@ export class VerifaydaService {
       code_challenge_method: 'S256',
       acr_values: this.faydaConfig.acrValues,
       claims_locales: this.faydaConfig.claimsLocales,
+      // Force a fresh authentication instead of silently reusing the eSignet
+      // SSO session. A booking can carry several passengers, each of whom must
+      // verify with their OWN Fayda; without this, the second and third
+      // "Verify with Fayda" clicks round-trip in a couple of seconds and hand
+      // back the first passenger's identity, which the booking flow then has to
+      // reject with no way for the user to authenticate as the right person.
+      prompt: 'login',
     });
 
     // Every claim is marked essential so eSignet shows them locked/pre-checked
diff --git a/apps/edr-passenger-web/portal/src/app/booking/passengers/page.tsx b/apps/edr-passenger-web/portal/src/app/booking/passengers/page.tsx
index 722ee75e2..ee681ab7e 100644
--- a/apps/edr-passenger-web/portal/src/app/booking/passengers/page.tsx
+++ b/apps/edr-passenger-web/portal/src/app/booking/passengers/page.tsx
@@ -761,6 +761,10 @@ function PassengersForm() {
             passportExpiryDate: stored.passportExpiryDate || '',
             passportIssuingAuthority: stored.passportIssuingAuthority || '',
             faydaVerified: stored.faydaVerified || false,
+            // Restore the identity that verified this passenger, so returning here from a
+            // later step (e.g. Back from /booking/seats) doesn't silently reopen the slot to
+            // an already-used Fayda.
+            faydaSub: stored.faydaSub || undefined,
             formExpanded: true,
           };
         }
@@ -873,13 +877,22 @@ function PassengersForm() {
         if (d?.verified) {
           const faydaSub: string | undefined = d.sub || d.faydaSub || d.fin;
 
-          // A single Fayda identity can't be reused across two different passengers.
-          const usedByOther = faydaSub && passengers.some(
-            (p, i) => i !== targetIndex && (p as any).faydaSub === faydaSub,
-          );
+          // A single Fayda identity can't be reused across two different passengers. Read the
+          // live form rather than the `passengers` captured when this effect was created — the
+          // snapshot restore repopulates the array as the form initializes.
+          const currentPassengers = watch('passengers') || [];
+          const conflictIndex = faydaSub
+            ? currentPassengers.findIndex(
+                (p, i) => i !== targetIndex && (p as any)?.faydaSub === faydaSub,
+              )
+            : -1;
 
-          if (usedByOther) {
-            setFaydaErrors((prev) => ({ ...prev, [targetIndex]: 'This Fayda identity is already linked to another passenger on this booking.' }));
+          if (conflictIndex >= 0) {
+            const conflictName = currentPassengers[conflictIndex]?.name?.trim();
+            setFaydaErrors((prev) => ({
+              ...prev,
+              [targetIndex]: `This Fayda ID has already been used to verify Passenger ${conflictIndex + 1}${conflictName ? ` (${conflictName})` : ''}. Each traveller must verify with their own Fayda.`,
+            }));
             setVerificationStatus((prev) => ({ ...prev, [targetIndex]: 'error' }));
           } else {
             // Convert "1980/12/01" → "1980-12-01"
@@ -989,6 +1002,13 @@ function PassengersForm() {
         const emailVal = pick(passengerData.email, user.email);
         if (emailVal) setValue('passengers.0.email', emailVal);
 
+        // A logged-in, already-verified user occupies slot 0 without going through a fresh
+        // Fayda round trip, so the callback never records their sub on the form. Seed it from
+        // the account here, otherwise the duplicate-identity check has nothing to compare
+        // against and the account holder can re-use their own Fayda on passenger 2.
+        const accountFaydaSub = pick(passengerData.faydaSub, (user as any).faydaSub);
+        if (accountFaydaSub) setValue('passengers.0.faydaSub', accountFaydaSub);
+
         if (mustVerifyFayda) {
           // Force the Fayda gate: leave name/DOB/gender empty and keep the form collapsed so the
           // "Verify with Fayda" screen is shown instead of an editable, pre-filled form.
@@ -1103,6 +1123,13 @@ function PassengersForm() {
         gender: p.gender,
         nationality: p.nationality,
         nationalId: p.nationalId,
+        // Carry the verified Fayda identity into the booking store so the duplicate-identity
+        // check still has it if the user comes back to this page from /booking/seats. Without
+        // it the restore path below rebuilds each passenger without a sub, and one Fayda could
+        // then re-verify every passenger. Stripped server-side by the global ValidationPipe
+        // (whitelist: true), so sending it to /passengers/save-details is a no-op there.
+        faydaVerified: p.faydaVerified,
+        faydaSub: p.faydaSub,
         passportNumber: p.passportNumber,
         passportCountry: p.passportCountry,
         passportIssueDate: p.passportIssueDate,