diff --git a/booking.py b/booking.py
index a3dd885..75855a1 100644
--- a/booking.py
+++ b/booking.py
@@ -264,11 +264,11 @@ class Booking(Workflow, ModelSQL, ModelView):
         res = []
         for folio in self.lines:
             if folio.invoice_line:
-                res.append(folio.invoice_line.id)
+                res.append(folio.invoice_line.invoice.id)
                 for charge in folio.charges:
                     if charge.invoice_line:
-                        res.append(charge.invoice_line.id)
-        return res
+                        res.append(charge.invoice_line.invoice.id)
+        return list(set(res))
 
     def get_person_num(self, name):
         res = 0