diff --git a/apps/api/src/app/import/import.service.spec.ts b/apps/api/src/app/import/import.service.spec.ts
index 5858cf0b65..05f609d788 100644
--- a/apps/api/src/app/import/import.service.spec.ts
+++ b/apps/api/src/app/import/import.service.spec.ts
@@ -456,6 +456,58 @@ describe('ImportService', () => {
         { dataSource: DataSource.YAHOO, symbol: 'AAPL' }
       ]);
     });
+
+    it('detects duplicate activities within the same import payload', async () => {
+      const activities = await importActivities({
+        activitiesDto: [
+          createActivityDto({
+            dataSource: DataSource.YAHOO,
+            date: '2024-01-01T00:00:00.000Z',
+            symbol: 'AAPL',
+            type: 'BUY'
+          }),
+          createActivityDto({
+            dataSource: DataSource.YAHOO,
+            date: '2024-01-01T00:00:00.000Z',
+            symbol: 'AAPL',
+            type: 'BUY'
+          })
+        ],
+        isDryRun: true
+      });
+
+      expect(activities[0].error).toBeUndefined();
+      expect(activities[1].error).toEqual({ code: 'IS_DUPLICATE' });
+    });
+
+    it('does not flag identical activities across different accounts as duplicates', async () => {
+      const activities = await importActivities({
+        activitiesDto: [
+          {
+            ...createActivityDto({
+              dataSource: DataSource.YAHOO,
+              date: '2024-01-01T00:00:00.000Z',
+              symbol: 'AAPL',
+              type: 'BUY'
+            }),
+            accountId: 'account-1'
+          },
+          {
+            ...createActivityDto({
+              dataSource: DataSource.YAHOO,
+              date: '2024-01-01T00:00:00.000Z',
+              symbol: 'AAPL',
+              type: 'BUY'
+            }),
+            accountId: 'account-2'
+          }
+        ],
+        isDryRun: true
+      });
+
+      expect(activities[0].error).toBeUndefined();
+      expect(activities[1].error).toBeUndefined();
+    });
   });
 
   function importActivities({
diff --git a/apps/api/src/app/import/import.service.ts b/apps/api/src/app/import/import.service.ts
index 0f44fc2855..53b4191da7 100644
--- a/apps/api/src/app/import/import.service.ts
+++ b/apps/api/src/app/import/import.service.ts
@@ -1045,6 +1045,9 @@ export class ImportService {
         withExcludedAccountsAndActivities: true
       });
 
+    const processedActivities: (Partial<Activity> &
+      Pick<Activity, 'assetProfile'>)[] = [];
+
     return activitiesDto.map(
       ({
         accountId,
@@ -1061,26 +1064,42 @@ export class ImportService {
       }) => {
         const date = parseISO(dateString);
 
-        const isDuplicate = existingActivities.some((activity) => {
-          return (
-            (activity.comment || null) === (comment || null) &&
-            (activity.currency === currency ||
-              activity.assetProfile.currency === currency) &&
-            activity.assetProfile.dataSource === dataSource &&
-            isSameSecond(activity.date, date) &&
-            activity.fee === fee &&
-            activity.quantity === quantity &&
-            activity.assetProfile.symbol === symbol &&
-            activity.type === type &&
-            activity.unitPrice === unitPrice
-          );
-        });
+        const isDuplicate =
+          existingActivities.some((activity) => {
+            return (
+              (!accountId || activity.accountId === accountId) &&
+              (activity.comment || null) === (comment || null) &&
+              ((activity.currency || null) === (currency || null) ||
+                activity.assetProfile.currency === currency) &&
+              activity.assetProfile.dataSource === dataSource &&
+              isSameSecond(activity.date, date) &&
+              activity.fee === fee &&
+              activity.quantity === quantity &&
+              activity.assetProfile.symbol === symbol &&
+              activity.type === type &&
+              activity.unitPrice === unitPrice
+            );
+          }) ||
+          processedActivities.some((activity) => {
+            return (
+              (!accountId || activity.accountId === accountId) &&
+              (activity.comment || null) === (comment || null) &&
+              (activity.currency || null) === (currency || null) &&
+              activity.assetProfile.dataSource === dataSource &&
+              isSameSecond(activity.date, date) &&
+              activity.fee === fee &&
+              activity.quantity === quantity &&
+              activity.assetProfile.symbol === symbol &&
+              activity.type === type &&
+              activity.unitPrice === unitPrice
+            );
+          });
 
         const error: ActivityError = isDuplicate
           ? { code: 'IS_DUPLICATE' }
           : undefined;
 
-        return {
+        const activityExtended = {
           accountId,
           comment,
           currency,
@@ -1107,6 +1126,12 @@ export class ImportService {
           },
           tagIds: tags
         };
+
+        if (!error) {
+          processedActivities.push(activityExtended);
+        }
+
+        return activityExtended;
       }
     );
   }