diff --git a/src/languages/en.ts b/src/languages/en.ts
index 75bfadee2ca7..1c15a62c2f73 100644
--- a/src/languages/en.ts
+++ b/src/languages/en.ts
@@ -9843,6 +9843,7 @@ const translations = {
         keepThisOne: 'Keep this one',
         confirmDetails: `Confirm the details you're keeping`,
         confirmDuplicatesInfo: `The duplicates you don't keep will be held for the submitter to delete.`,
+        cannotMergeDuplicates: 'You can only merge expenses on reports that are open or pending first approval. You may need to retract the report, merge the expenses, then resubmit.',
         hold: 'This expense was put on hold',
         resolvedDuplicates: 'resolved the duplicate',
         companyCardRequired: 'Company card purchases required',
diff --git a/src/languages/es.ts b/src/languages/es.ts
index 5e173ef30b78..e2dfef35175c 100644
--- a/src/languages/es.ts
+++ b/src/languages/es.ts
@@ -9885,6 +9885,7 @@ El plan Controlar empieza en 9 $ por miembro activo al mes.`,
         keepThisOne: 'Mantener éste',
         confirmDetails: 'Confirma los detalles que conservas',
         confirmDuplicatesInfo: 'Los duplicados que no conserves se mantendrán para que el remitente los elimine.',
+        cannotMergeDuplicates: 'Solo puedes combinar gastos en informes que estén abiertos o pendientes de la primera aprobación. Es posible que debas retirar el informe, combinar los gastos y luego volver a enviarlo.',
         hold: 'Este gasto está retenido',
         resolvedDuplicates: 'resolvió el duplicado',
         companyCardRequired: 'Se requieren compras con la tarjeta de la empresa.',
diff --git a/src/libs/TransactionUtils/index.ts b/src/libs/TransactionUtils/index.ts
index 879516700609..841cf56c778e 100644
--- a/src/libs/TransactionUtils/index.ts
+++ b/src/libs/TransactionUtils/index.ts
@@ -32,8 +32,8 @@ import {
     isCurrentUserSubmitter,
     isInvoiceReport,
     isOpenExpenseReport,
+    isOpenReport,
     isProcessingReport,
-    isReportIDApproved,
     isSelfDM,
     isSettled,
     isThread,
@@ -2589,8 +2589,19 @@ function removeTransactionFromDuplicateTransactionViolation(
     }
 }
 
+/**
+ * Keeps only transactions that Auth's MergeTransactions command would accept, i.e. those whose report is still
+ * open or awaiting first-level approval. Anything approved, closed (Submit & Close), or reimbursed is rejected
+ * server-side, so filtering here prevents sending a merge request that would fail.
+ */
 function removeSettledAndApprovedTransactions(transactions: Array<OnyxEntry<Transaction>>): Transaction[] {
-    return transactions.filter((transaction) => !!transaction && !isSettled(transaction?.reportID) && !isReportIDApproved(transaction?.reportID)) as Transaction[];
+    return transactions.filter((transaction) => {
+        if (!transaction) {
+            return false;
+        }
+        const report = getReportOrDraftReport(transaction.reportID);
+        return isOpenReport(report) || isProcessingReport(report);
+    }) as Transaction[];
 }
 
 /**
diff --git a/src/pages/TransactionDuplicate/Confirmation.tsx b/src/pages/TransactionDuplicate/Confirmation.tsx
index 1703fb5b7eae..4643ea16b6a2 100644
--- a/src/pages/TransactionDuplicate/Confirmation.tsx
+++ b/src/pages/TransactionDuplicate/Confirmation.tsx
@@ -1,6 +1,7 @@
 import FullPageNotFoundView from '@components/BlockingViews/FullPageNotFoundView';
 import Button from '@components/ButtonComposed';
 import FixedFooter from '@components/FixedFooter';
+import FormHelpMessage from '@components/FormHelpMessage';
 import FullScreenLoadingIndicator from '@components/FullscreenLoadingIndicator';
 import HeaderWithBackButton from '@components/HeaderWithBackButton';
 import MoneyRequestView from '@components/ReportActionItem/MoneyRequestView';
@@ -44,7 +45,7 @@ import isLoadingOnyxValue from '@src/types/utils/isLoadingOnyxValue';
 import type {OnyxEntry} from 'react-native-onyx';
 
 import {useRoute} from '@react-navigation/native';
-import React, {useCallback, useMemo, useRef} from 'react';
+import React, {useCallback, useMemo, useRef, useState} from 'react';
 import {View} from 'react-native';
 
 function Confirmation() {
@@ -113,6 +114,7 @@ function Confirmation() {
         };
     }, [reviewDuplicatesTaxCode, reviewDuplicatesTaxAmount, taxRates, duplicatedTransactionTaxCode]);
     const isReportOwner = iouReport?.ownerAccountID === currentUserPersonalDetails?.accountID;
+    const [mergeErrorMessage, setMergeErrorMessage] = useState('');
     const currentUserAccountID = currentUserPersonalDetails.accountID;
     const currentUserLogin = currentUserPersonalDetails?.login;
     const childReportID = reportAction?.childReportID;
@@ -221,14 +223,30 @@ function Confirmation() {
                         </ShowContextMenuStateContext.Provider>
                     </ScrollView>
                     <FixedFooter style={styles.mtAuto}>
+                        {!!mergeErrorMessage && (
+                            <FormHelpMessage
+                                message={mergeErrorMessage}
+                                style={styles.mb3}
+                            />
+                        )}
                         <Button
                             variant={CONST.BUTTON_VARIANT.SUCCESS}
                             onPress={() => {
-                                isDismissingRef.current = true;
                                 if (!isReportOwner) {
+                                    isDismissingRef.current = true;
                                     handleResolveDuplicates();
                                     return;
                                 }
+                                // Auth's MergeTransactions only accepts a merge when the kept expense's report is still
+                                // editable and there is at least one duplicate to merge, so block it here and explain
+                                // rather than failing server-side.
+                                const isKeptReportMergeable = ReportUtils.isOpenReport(iouReport) || ReportUtils.isProcessingReport(iouReport);
+                                if (!isKeptReportMergeable || transactionsMergeParams.transactionIDList.length === 0) {
+                                    setMergeErrorMessage(translate('violations.cannotMergeDuplicates'));
+                                    return;
+                                }
+                                setMergeErrorMessage('');
+                                isDismissingRef.current = true;
                                 handleMergeDuplicates();
                             }}
                             size={CONST.BUTTON_SIZE.LARGE}