diff --git a/core/apps/finance/serializers/cash_transaction.py b/core/apps/finance/serializers/cash_transaction.py
index 6164bbb..8d1abee 100644
--- a/core/apps/finance/serializers/cash_transaction.py
+++ b/core/apps/finance/serializers/cash_transaction.py
@@ -65,7 +65,7 @@ class CashTransactionUpdateSerializer(serializers.ModelSerializer):
         if project_ids:
             projects = Project.objects.filter(id__in=project_ids)
             instance.projects.clear()
-            instance.projects.set(projects)
+            instance.projects.add(*projects)        
         
         instance.save()
         return instance