diff --git a/ReportImp/AutismusKoelnBonn/Invoicing/CustomInvoiceNumberGenerator.cs b/ReportImp/AutismusKoelnBonn/Invoicing/CustomInvoiceNumberGenerator.cs
index d5e0dcfad..0b4afe849 100644
--- a/ReportImp/AutismusKoelnBonn/Invoicing/CustomInvoiceNumberGenerator.cs
+++ b/ReportImp/AutismusKoelnBonn/Invoicing/CustomInvoiceNumberGenerator.cs
@@ -54,8 +54,8 @@ namespace AutismusKoelnBonn.Invoicing
         {
             string next = base.ApplyPatternWithId(pattern, number, id);
 
-            next = next.Replace("{AM}", invoiceBase.AccountingPeriodEnd.Value.Month.ToString());
-            next = next.Replace("{AJ}", string.Format("{0:yy}", invoiceBase.AccountingPeriodEnd.Value));
+            next = next.Replace("{AM}", invoiceBase.AccountingPeriodEnd.Value.Month.ToString()); // Abrechnungsmonat (Letzter des Zeitraums)
+            next = next.Replace("{AJ}", string.Format("{0:yy}", invoiceBase.AccountingPeriodEnd.Value)); // Abrechnungsjahr
 
             return next;
         }