diff --git a/src/app-gocardless/bank-factory.js b/src/app-gocardless/bank-factory.js
index 1d5d33c70..831c694ec 100644
--- a/src/app-gocardless/bank-factory.js
+++ b/src/app-gocardless/bank-factory.js
@@ -8,6 +8,7 @@ import IngIngddeff from './banks/ing-ingddeff.js';
 import IngPlIngbplpw from './banks/ing-pl-ingbplpw.js';
 import IntegrationBank from './banks/integration-bank.js';
 import MbankRetailBrexplpw from './banks/mbank-retail-brexplpw.js';
+import NationwideNaiaGB21 from './banks/nationwide-naiagb21.js';
 import NorwegianXxNorwnok1 from './banks/norwegian-xx-norwnok1.js';
 import SEBKortBankAB from './banks/seb-kort-bank-ab.js';
 import SEBPrivat from './banks/seb-privat.js';
@@ -27,6 +28,7 @@ export const banks = [
   IngIngddeff,
   IngPlIngbplpw,
   MbankRetailBrexplpw,
+  NationwideNaiaGB21,
   NorwegianXxNorwnok1,
   SEBKortBankAB,
   SEBPrivat,
diff --git a/src/app-gocardless/banks/nationwide-naiagb21.js b/src/app-gocardless/banks/nationwide-naiagb21.js
new file mode 100644
index 000000000..13908dbd3
--- /dev/null
+++ b/src/app-gocardless/banks/nationwide-naiagb21.js
@@ -0,0 +1,47 @@
+import Fallback from './integration-bank.js';
+
+/** @type {import('./bank.interface.js').IBank} */
+export default {
+  ...Fallback,
+
+  institutionIds: ['NATIONWIDE_NAIAGB21'],
+
+  accessValidForDays: 90,
+
+  normalizeTransaction(transaction, booked) {
+    // Nationwide returns pending transactions with a date representing
+    // the latest a transaction could be booked. This stops actual's
+    // deduplication logic from working as it only checks 7 days ahead/behind
+    // and the transactionID from Nationwide changes when a transaction is
+    // booked
+    if (!booked) {
+      const d = new Date(transaction.bookingDate);
+      d.setDate(d.getDate() - 8);
+
+      const useDate = new Date(Math.min(d.getTime(), new Date().getTime()));
+
+      transaction.bookingDate = useDate.toISOString().slice(0, 10);
+    }
+
+    console.log(transaction);
+
+    // Nationwide also occasionally returns erroneous transaction_ids
+    // that are malformed and can even change after import. This will ignore
+    // these ids and unset them. When a correct ID is returned then it will
+    // update via the deduplication logic
+    const debitCreditRegex = /^00(DEB|CRED)IT.+$/;
+    const validLengths = [
+      40, // Nationwide credit cards
+      32, // Nationwide current accounts
+    ];
+
+    if (
+      transaction.transactionId?.match(debitCreditRegex) ||
+      !validLengths.includes(transaction.transactionId?.length)
+    ) {
+      transaction.transactionId = null;
+    }
+
+    return Fallback.normalizeTransaction(transaction, booked);
+  },
+};
diff --git a/src/app-gocardless/banks/tests/nationwide-naiagb21.spec.js b/src/app-gocardless/banks/tests/nationwide-naiagb21.spec.js
new file mode 100644
index 000000000..5dc549528
--- /dev/null
+++ b/src/app-gocardless/banks/tests/nationwide-naiagb21.spec.js
@@ -0,0 +1,105 @@
+import Nationwide from '../nationwide-naiagb21.js';
+import { mockTransactionAmount } from '../../services/tests/fixtures.js';
+
+describe('Nationwide', () => {
+  describe('#normalizeTransaction', () => {
+    it('retains date for booked transaction', () => {
+      const d = new Date();
+      d.setDate(d.getDate() - 7);
+
+      const date = d.toISOString().split('T')[0];
+
+      const transaction = {
+        bookingDate: date,
+        transactionAmount: mockTransactionAmount,
+      };
+
+      const normalizedTransaction = Nationwide.normalizeTransaction(
+        transaction,
+        true,
+      );
+
+      expect(normalizedTransaction.date).toEqual(date);
+    });
+
+    it('fixes date for pending transactions', () => {
+      const d = new Date();
+      const date = d.toISOString().split('T')[0];
+
+      const transaction = {
+        bookingDate: date,
+        transactionAmount: mockTransactionAmount,
+      };
+
+      const normalizedTransaction = Nationwide.normalizeTransaction(
+        transaction,
+        false,
+      );
+
+      expect(new Date(normalizedTransaction.date).getTime()).toBeLessThan(
+        d.getTime(),
+      );
+    });
+
+    it('keeps transactionId if in the correct format', () => {
+      const transactionId = 'a896729bb8b30b5ca862fe70bd5967185e2b5d3a';
+      const transaction = {
+        bookingDate: '2024-01-01T00:00:00Z',
+        transactionId,
+        transactionAmount: mockTransactionAmount,
+      };
+
+      const normalizedTransaction = Nationwide.normalizeTransaction(
+        transaction,
+        false,
+      );
+
+      expect(normalizedTransaction.transactionId).toBe(transactionId);
+    });
+
+    it('unsets transactionId if not valid length', () => {
+      const transaction = {
+        bookingDate: '2024-01-01T00:00:00Z',
+        transactionId: '0123456789',
+        transactionAmount: mockTransactionAmount,
+      };
+
+      const normalizedTransaction = Nationwide.normalizeTransaction(
+        transaction,
+        false,
+      );
+
+      expect(normalizedTransaction.transactionId).toBeNull();
+    });
+
+    it('unsets transactionId if debit placeholder found', () => {
+      const transaction = {
+        bookingDate: '2024-01-01T00:00:00Z',
+        transactionId: '00DEBIT202401010000000000-1000SUPERMARKET',
+        transactionAmount: mockTransactionAmount,
+      };
+
+      const normalizedTransaction = Nationwide.normalizeTransaction(
+        transaction,
+        false,
+      );
+
+      expect(normalizedTransaction.transactionId).toBeNull();
+    });
+
+    it('unsets transactionId if credit placeholder found', () => {
+      const transaction = {
+        bookingDate: '2024-01-01T00:00:00Z',
+        transactionId: '00CREDIT202401010000000000-1000SUPERMARKET',
+        transactionAmount: mockTransactionAmount,
+      };
+
+      const normalizedTransaction = Nationwide.normalizeTransaction(
+        transaction,
+        false,
+      );
+
+      expect(normalizedTransaction.transactionId).toBeNull();
+    });
+  });
+});
diff --git a/upcoming-release-notes/372.md b/upcoming-release-notes/372.md
new file mode 100644
index 000000000..ed761a219
--- /dev/null
+++ b/upcoming-release-notes/372.md
@@ -0,0 +1,6 @@
+---
+category: Enhancements
+authors: [matt-fidd]
+---
+
+Add bank handler for NATIONWIDE_NAIAGB21 (Nationwide) for more accurate dates and to fix duplicate transaction issues