diff --git a/core/apps/finance/serializers/cash_transaction.py b/core/apps/finance/serializers/cash_transaction.py
index cde8aca..6164bbb 100644
--- a/core/apps/finance/serializers/cash_transaction.py
+++ b/core/apps/finance/serializers/cash_transaction.py
@@ -64,6 +64,7 @@ class CashTransactionUpdateSerializer(serializers.ModelSerializer):
         project_ids = validated_data.pop('project_ids', [])
         if project_ids:
             projects = Project.objects.filter(id__in=project_ids)
+            instance.projects.clear()
             instance.projects.set(projects)
         
         instance.save()