diff --git a/apps/transaction/views.py b/apps/transaction/views.py
index bc2aebf..e0df7c1 100644
--- a/apps/transaction/views.py
+++ b/apps/transaction/views.py
@@ -182,6 +182,20 @@ class TransactionParticipantCreateView(generics.CreateAPIView):
         )
         print(f'--->  {type(transaction_participant)}/ {transaction_participant}')    
 
+        # 5. Update user birthdate based on participant infos
+        validated_participant_infos = serializer.validated_data.get('participant_infos', [])
+        for info in validated_participant_infos:
+            email = info.get('email')
+            birthdate = info.get('birthdate')
+            if email and birthdate:
+                try:
+                    target_user = User.objects.filter(email__iexact=email.strip()).first()
+                    if target_user:
+                        target_user.birthdate = birthdate
+                        target_user.save(update_fields=['birthdate'])
+                except Exception as e:
+                    print(f"Error updating user birthdate: {e}")
+
         # =======================================================
         # NEW LOGIC: HYBRID GEOLOCATION CHECK (Cloudflare + Local DB)
         # =======================================================