diff --git a/src/libs/actions/IOU.js b/src/libs/actions/IOU.js
index 9056210024bc..111ee8e32b28 100644
--- a/src/libs/actions/IOU.js
+++ b/src/libs/actions/IOU.js
@@ -4,7 +4,7 @@ import CONST from '../../CONST';
 import ONYXKEYS from '../../ONYXKEYS';
 import ROUTES from '../../ROUTES';
 import * as API from '../API';
-import {getSimplifiedIOUReport, fetchChatReportsByIDs, fetchIOUReportByIDAndUpdateChatReport} from './Report';
+import {getSimplifiedIOUReport, syncChatAndIOUReports} from './Report';
 import Navigation from '../Navigation/Navigation';
 import asyncOpenURL from '../asyncOpenURL';
 
@@ -135,14 +135,10 @@ function rejectTransaction({
             if (response.jsonCode !== 200) {
                 throw new Error(`${response.code} ${response.message}`);
             }
-            fetchChatReportsByIDs([chatReportID]);
-
-            // If an iouReport is open (has an IOU, but is not yet paid) then we sync the chatReport's 'iouReportID'
-            // field in Onyx, simplifying IOU data retrieval and reducing necessary API calls when displaying IOU
-            // components. If we didn't sync the reportIDs, the transaction would still be shown to users as rejectable
-            // The iouReport being fetched here must be open, because only an open iouReoport can be paid. Therefore,
-            // we should also sync the chatReport after fetching the iouReport.
-            fetchIOUReportByIDAndUpdateChatReport(reportID, chatReportID);
+
+            const chatReport = response.reports[chatReportID];
+            const iouReport = response.reports[reportID];
+            syncChatAndIOUReports(chatReport, iouReport);
         })
         .catch(error => console.error(`Error rejecting transaction: ${error}`))
         .finally(() => {
@@ -212,14 +208,10 @@ function payIOUReport({
             if (response.jsonCode !== 200) {
                 throw new Error(response.message);
             }
-            fetchChatReportsByIDs([chatReportID]);
-
-            // If an iouReport is open (has an IOU, but is not yet paid) then we sync the chatReport's 'iouReportID'
-            // field in Onyx, simplifying IOU data retrieval and reducing necessary API calls when displaying IOU
-            // components. If we didn't sync the reportIDs, the paid IOU would still be shown to users as unpaid. The
-            // iouReport being fetched here must be open, because only an open iouReoport can be paid.
-            // Therefore, we should also sync the chatReport after fetching the iouReport.
-            fetchIOUReportByIDAndUpdateChatReport(reportID, chatReportID);
+
+            const chatReportStuff = response.reports[chatReportID];
+            const iouReportStuff = response.reports[reportID];
+            syncChatAndIOUReports(chatReportStuff, iouReportStuff);
         })
         .catch((error) => {
             console.error(`Error Paying iouReport: ${error}`);
diff --git a/src/libs/actions/Report.js b/src/libs/actions/Report.js
index 9ebc42db9629..2ee0440e117a 100644
--- a/src/libs/actions/Report.js
+++ b/src/libs/actions/Report.js
@@ -1080,7 +1080,7 @@ function deleteReportComment(reportID, reportAction) {
     const sequenceNumber = reportAction.sequenceNumber;
     const reportActionsToMerge = {};
     const oldMessage = {...reportAction.message};
-    reportActionsToMerge[reportAction.sequenceNumber] = {
+    reportActionsToMerge[sequenceNumber] = {
         ...reportAction,
         message: [
             {
@@ -1269,6 +1269,40 @@ function saveReportActionDraft(reportID, reportActionID, draftMessage) {
     Onyx.set(`${ONYXKEYS.COLLECTION.REPORT_ACTIONS_DRAFTS}${reportID}_${reportActionID}`, draftMessage);
 }
 
+/**
+ * Syncs up a chat report and an IOU report in Onyx after an IOU transaction has been made
+ * by setting the iouReportID and hasOutstandingIOU for the chat report.
+ * Even though both reports are updated in the back-end, the API doesn't handle syncing their reportIDs.
+ * If we didn't sync these reportIDs, the paid IOU would still be shown to users as unpaid.
+ * The iouReport being fetched here must be open, because only an open iouReport can be paid.
+ *
+ * @param {Object} chatReport
+ * @param {Object} iouReport
+ */
+function syncChatAndIOUReports(chatReport, iouReport) {
+    // Return early in case there's a back-end issue preventing the IOU command from returning the report objects.
+    if (!chatReport || !iouReport) {
+        return;
+    }
+
+    const simplifiedIouReport = {};
+    const simplifiedReport = {};
+    const chatReportKey = `${ONYXKEYS.COLLECTION.REPORT}${chatReport.reportID}`;
+    const iouReportKey = `${ONYXKEYS.COLLECTION.REPORT_IOUS}${iouReport.reportID}`;
+
+    // We don't want to sync an iou report that's already been reimbursed with its chat report.
+    if (!iouReport.stateNum === CONST.REPORT.STATE_NUM.SUBMITTED) {
+        simplifiedReport[chatReportKey].iouReportID = iouReport.reportID;
+    }
+    simplifiedReport[chatReportKey] = getSimplifiedReportObject(chatReport);
+    simplifiedReport[chatReportKey].hasOutstandingIOU = iouReport.stateNum
+        === (CONST.REPORT.STATE_NUM.PROCESSING && iouReport.total !== 0);
+    simplifiedIouReport[iouReportKey] = getSimplifiedIOUReport(iouReport, chatReport.reportID);
+
+    Onyx.mergeCollection(ONYXKEYS.COLLECTION.REPORT_IOUS, simplifiedIouReport);
+    Onyx.mergeCollection(ONYXKEYS.COLLECTION.REPORT, simplifiedReport);
+}
+
 /**
  * Updates a user's notification preferences for a chat room
  *
@@ -1302,4 +1336,5 @@ export {
     saveReportActionDraft,
     deleteReportComment,
     getSimplifiedIOUReport,
+    syncChatAndIOUReports,
 };