diff --git a/fet2020/finance/forms.py b/fet2020/finance/forms.py
index fa0507c6..b24265aa 100644
--- a/fet2020/finance/forms.py
+++ b/fet2020/finance/forms.py
@@ -400,6 +400,16 @@ class BillAdminForm(forms.ModelForm):
         # delete wiref id from if status is not opened.
         qs = qs.filter(status=Wiref.Status.OPENED)
 
+        # add wiref id if wiref is already transferred.
+        bill = kwargs.get("instance", None)
+        if bill is not None and bill.wiref is not None and bill.wiref.status != Wiref.Status.OPENED:
+            qs |= self.fields["wiref"].queryset.filter(wiref_id=bill.wiref.wiref_id)
+
+            self.fields["wiref"].disabled = True
+            self.fields["wiref"].widget.can_add_related = False
+            self.fields["wiref"].widget.can_change_related = False
+            self.fields["wiref"].widget.can_delete_related = False
+
         self.fields["wiref"].queryset = qs.order_by("-wiref_id")