diff --git a/src/views/payments/PaymentListView.vue b/src/views/payments/PaymentListView.vue
index 8942fcd..1efb7ca 100644
--- a/src/views/payments/PaymentListView.vue
+++ b/src/views/payments/PaymentListView.vue
@@ -117,11 +117,16 @@
         </div>
 
         <!-- Duplicate Payment Warning -->
-        <div v-if="duplicateWarning?.hasDuplicate" class="p-3 bg-yellow-50 border-round border-1 border-yellow-400 text-yellow-900 text-sm flex align-items-start gap-2">
-          <i class="pi pi-exclamation-triangle text-yellow-600 text-lg mt-1 flex-shrink-0"></i>
+        <div
+          v-if="duplicateWarning && duplicateWarning.hasDuplicate"
+          class="p-3 border-round flex align-items-start gap-2 duplicate-warning-box"
+        >
+          <i class="pi pi-exclamation-triangle text-xl text-yellow-400 mt-1 flex-shrink-0"></i>
           <div class="flex flex-column gap-1">
-            <span class="font-bold">هشدار: صورتحساب تکراری</span>
-            <span>برای این دانشجو قبلاً در کلاس‌های انتخاب‌شده صورتحساب ثبت شده است.</span>
+            <span class="font-bold text-yellow-300 text-sm">هشدار: برای این دانشجو قبلاً در این کلاس صورتحساب ثبت شده است.</span>
+            <span class="text-xs text-yellow-200" v-if="duplicateWarning.payments && duplicateWarning.payments.length">
+              صورتحساب قبلی با کد {{ duplicateWarning.payments.map(p => p.uniqueCode || p._id).join('، ') }} موجود است.
+            </span>
           </div>
         </div>
 
@@ -270,7 +275,7 @@
 </template>
 
 <script setup>
-import { ref, reactive, computed, onMounted } from 'vue';
+import { ref, reactive, computed, watch, onMounted } from 'vue';
 import { useDataTable } from '@/composables/useDataTable';
 import { usePersianDate } from '@/composables/usePersianDate';
 import { useToast } from '@/composables/useToast';
@@ -386,22 +391,39 @@ const eligibleUsers = computed(() => {
   return usersList.value.filter((u) => eligibleIds?.has(String(u._id || u.id)));
 });
 
-const checkDuplicateInvoice = async () => {
-  if (!createForm.user || !createForm.classes?.length) {
+const checkDuplicateInvoice = async (userIdVal = null) => {
+  const targetUser = userIdVal || createForm.user;
+  if (!targetUser || !createForm.classes || !createForm.classes.length) {
     duplicateWarning.value = null;
     return;
   }
   try {
+    const classIds = Array.isArray(createForm.classes)
+      ? createForm.classes.map((c) => c?._id || c?.id || c).join(',')
+      : String(createForm.classes);
     const res = await paymentApi.checkDuplicate({
-      userId: createForm.user,
-      classes: createForm.classes.join(',')
+      userId: String(targetUser?._id || targetUser?.id || targetUser),
+      classes: classIds
     });
     duplicateWarning.value = res.data?.data || res.data || res;
   } catch (err) {
+    console.error('checkDuplicateInvoice error:', err);
     duplicateWarning.value = null;
   }
 };
 
+watch(
+  [() => createForm.user, () => createForm.classes],
+  async ([newUser, newClasses]) => {
+    if (newUser && newClasses && newClasses.length) {
+      await checkDuplicateInvoice(newUser);
+    } else {
+      duplicateWarning.value = null;
+    }
+  },
+  { deep: true, immediate: true }
+);
+
 const onClassesSelected = async () => {
   if (createForm.user && !eligibleUsers.value.some((u) => (u._id || u.id) === createForm.user)) {
     createForm.user = null;
@@ -639,3 +661,11 @@ onMounted(() => {
   fetchDropdownData();
 });
 </script>
+
+<style scoped>
+.duplicate-warning-box {
+  background: rgba(234, 179, 8, 0.15) !important;
+  border: 1px solid rgba(234, 179, 8, 0.6) !important;
+  color: #fef08a !important;
+}
+</style>