diff --git a/src/adaptermanager.js b/src/adaptermanager.js
index 4c8ae95b3f7..71683014618 100644
--- a/src/adaptermanager.js
+++ b/src/adaptermanager.js
@@ -29,6 +29,7 @@ function getBids({bidderCode, requestId, bidderRequestId, adUnits}) {
         return Object.assign(bid, {
           placementCode: adUnit.code,
           mediaType: adUnit.mediaType,
+          transactionId : adUnit.transactionId,
           sizes: sizes,
           bidId: utils.getUniqueIdentifierStr(),
           bidderRequestId,
diff --git a/src/prebid.js b/src/prebid.js
index d22dd462373..c5811ade561 100644
--- a/src/prebid.js
+++ b/src/prebid.js
@@ -429,9 +429,13 @@ $$PREBID_GLOBAL$$.requestBids = function ({ bidsBackHandler, timeout, adUnits, a
 $$PREBID_GLOBAL$$.addAdUnits = function (adUnitArr) {
   utils.logInfo('Invoking $$PREBID_GLOBAL$$.addAdUnits', arguments);
   if (utils.isArray(adUnitArr)) {
-    //append array to existing
+    // generate transactionid for each new adUnits
+    // Append array to existing
+    adUnitArr.forEach(adUnit => adUnit.transactionId = utils.generateUUID());
     $$PREBID_GLOBAL$$.adUnits.push.apply($$PREBID_GLOBAL$$.adUnits, adUnitArr);
   } else if (typeof adUnitArr === objectType_object) {
+    // Generate the transaction id for the adunit
+    adUnitArr.transactionId = utils.generateUUID();
     $$PREBID_GLOBAL$$.adUnits.push(adUnitArr);
   }
 };
diff --git a/test/fixtures/fixtures.js b/test/fixtures/fixtures.js
index 75a90bb2b42..202d95b402b 100644
--- a/test/fixtures/fixtures.js
+++ b/test/fixtures/fixtures.js
@@ -28,7 +28,8 @@ export function getBidRequests() {
           "bidderRequestId": "2946b569352ef2",
           "requestId": "1863e370099523",
           "startTime": 1462918897462,
-          "status": 1
+          "status": 1,
+          "transactionId": "fsafsa"
         },
         {
           "bidder": "appnexus",
@@ -50,7 +51,8 @@ export function getBidRequests() {
           "bidderRequestId": "2946b569352ef2",
           "requestId": "1863e370099523",
           "startTime": 1462918897463,
-          "status": 1
+          "status": 1,
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897460
@@ -79,7 +81,8 @@ export function getBidRequests() {
           ],
           "bidId": "6d11aa2d5b3659",
           "bidderRequestId": "5e1525bae3eb11",
-          "requestId": "1863e370099523"
+          "requestId": "1863e370099523",
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897463
@@ -112,7 +115,7 @@ export function getBidRequests() {
             "sizes": [
               15,
               10
-            ]
+            ],
           },
           "placementCode": "/19968336/header-bid-tag-0",
           "sizes": [
@@ -127,7 +130,8 @@ export function getBidRequests() {
           ],
           "bidId": "96aff279720d39",
           "bidderRequestId": "8778750ee15a77",
-          "requestId": "1863e370099523"
+          "requestId": "1863e370099523",
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897474
@@ -156,7 +160,8 @@ export function getBidRequests() {
           "bidId": "1144e2f0de84363",
           "bidderRequestId": "107f5e6e98dcf09",
           "requestId": "1863e370099523",
-          "startTime": 1462918897477
+          "startTime": 1462918897477,
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897475
@@ -185,7 +190,8 @@ export function getBidRequests() {
           "bidId": "135e89c039705da",
           "bidderRequestId": "12eeded736650b4",
           "requestId": "1863e370099523",
-          "status": 1
+          "status": 1,
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897477
@@ -215,7 +221,8 @@ export function getBidRequests() {
           "bidderRequestId": "167c4d79b615948",
           "requestId": "1863e370099523",
           "startTime": 1462918897480,
-          "status": 1
+          "status": 1,
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897479
@@ -245,7 +252,8 @@ export function getBidRequests() {
           "bidderRequestId": "18bed198c172a69",
           "requestId": "1863e370099523",
           "startTime": 1462918897481,
-          "status": 1
+          "status": 1,
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897480
@@ -273,7 +281,8 @@ export function getBidRequests() {
           ],
           "bidId": "21ae8131ec04f6e",
           "bidderRequestId": "20d0d30333715a7",
-          "requestId": "1863e370099523"
+          "requestId": "1863e370099523",
+          "transactionId": "fsafsa"
         }
       ],
       "start": 1462918897482
diff --git a/test/spec/adUnits_spec.js b/test/spec/adUnits_spec.js
index f3e5fd67d16..280ccc1eb16 100644
--- a/test/spec/adUnits_spec.js
+++ b/test/spec/adUnits_spec.js
@@ -83,6 +83,13 @@ describe('Publisher API _ AdUnits', function () {
       assert.strictEqual(bids2[1].params.placementId, '827326', 'adUnit2 bids2 params.placementId');
     });
 
+    it ('both add unit should contains a transactionid.'), function() {
+      assert.exist(adUnit1.transationId)
+      assert.exist(adUnit2.transationId)
+
+      assert.strictEqual(false, adUnit1.transationId === adUnit2.transationId)
+    }
+
     it('the second adUnits value should be same with the adUnits that is added by $$PREBID_GLOBAL$$.addAdUnits();', function () {
 
       assert.strictEqual(adUnit2.code, '/1996833/slot-2', 'adUnit2 code');