diff --git a/ReportImp/DomizielAnsbach/Invoicing/ZVInvoiceCreation.cs b/ReportImp/DomizielAnsbach/Invoicing/ZVInvoiceCreation.cs
index 4b54b0062..d251af175 100644
--- a/ReportImp/DomizielAnsbach/Invoicing/ZVInvoiceCreation.cs
+++ b/ReportImp/DomizielAnsbach/Invoicing/ZVInvoiceCreation.cs
@@ -306,6 +306,16 @@ namespace DomizielAnsbach.Invoicing
             //return newlist;
         }
 
+        public override string GetSummaryItemKey(SupportConceptApprovalPeriod scap, InvoiceItem iitem, bool summaryPerMonth)
+        {
+            String key = String.Format("{0}_{1}_{2}", iitem.AmountPerUnit, iitem.ItemDescription, iitem.RateFactor);
+            if (summaryPerMonth)
+            {
+                key = String.Format("{0}_{1}_{2}_{3:yyyyMM}", iitem.AmountPerUnit, iitem.ItemDescription, iitem.RateFactor, iitem.ItemPeriodStart);
+            }
+            return key;
+        }
+
         private InvoiceItem CreateFahrtkostenZulageItem(List<ServiceRecordDC> serviceRecordsInPeriod, DateTimeSpan invoicePeriod, SupportConceptApprovalPeriod scap, ZuverdienstHelper.AktuellePauschalen pausch)
         {
             decimal? pauschale;