diff --git a/src/actions/ebs-sync/ebs.js b/src/actions/ebs-sync/ebs.js
index 618fa9a..bb6ba6a 100644
--- a/src/actions/ebs-sync/ebs.js
+++ b/src/actions/ebs-sync/ebs.js
@@ -55,7 +55,7 @@ import { resolveVbndReasonCode } from './discount-reason-codes.js';
 const TRANSIENT_ERROR_PATTERN = /timeout|timed out|aborted|fetch failed|network|ECONNRESET|ENOTFOUND|ETIMEDOUT|EAI_AGAIN/i;
 
 const CHASE_AVS_UNVALIDATED_CODES = new Set([
-  '1', '2', '3', '4', '5', '6', '8', 'G', 'J', 'M1', 'M8', 'N4', 'N6', 'R', 'UK',
+  '1', '2', '3', '4', '5', '6', '8', 'G', 'J', 'M1', 'M8', 'N4', 'N6', 'R', 'UK', 'UNKNOWN',
 ]);
 
 /**
@@ -436,7 +436,7 @@ function resolveShippingIsValidated(order) {
 function resolveBillingIsValidated(paymentSnapshot) {
   if (paymentSnapshot?.method !== 'chasehpp') return true;
   if (Number(paymentSnapshot.amount || 0) === 0) return true;
-  return !CHASE_AVS_UNVALIDATED_CODES.has(String(paymentSnapshot.avsMatch || '').trim());
+  return !CHASE_AVS_UNVALIDATED_CODES.has(String(paymentSnapshot.avsMatch || '').trim().toUpperCase());
 }
 
 /**
diff --git a/test/ebs-sync/ebs-e2e.test.js b/test/ebs-sync/ebs-e2e.test.js
index c38e73f..7ea235b 100644
--- a/test/ebs-sync/ebs-e2e.test.js
+++ b/test/ebs-sync/ebs-e2e.test.js
@@ -631,7 +631,7 @@ describe('ebs-sync e2e', () => {
       expect(addressValidation(xml, 'BillTo')).toBe('true');
     });
 
-    test.each(['1', '2 ', 'G', 'M1', 'UK'])('BillTo IsValidated is false for Chase AVS %s', async (avsMatch) => {
+    test.each(['1', '2 ', 'G', 'M1', 'UK', 'Unknown'])('BillTo IsValidated is false for Chase AVS %s', async (avsMatch) => {
       const xml = await buildXml(
         clone(CC_APPROVED_ORDER),
         withCompletedPayment(loadJournal('journal-cc-approved.ndjson'), { avsMatch }),