diff --git a/Service/Plugins/AccountingService.cs b/Service/Plugins/AccountingService.cs
index 98b2fba21..63c802fb9 100644
--- a/Service/Plugins/AccountingService.cs
+++ b/Service/Plugins/AccountingService.cs
@@ -97,9 +97,10 @@ namespace BeWo.Service.Plugins
 		protected virtual ServiceInvoiceDC ErstelleDifferenzRechnung(DifferenzRechnungCheck item)
         {
 			ServiceInvoiceDC diffRechnung = null;
-			var alterBetrag = item.VorhandeneRechungen.Sum(i => i.ClaimSum ?? 0);
+			//var alterBetrag = item.VorhandeneRechungen.Sum(i => i.ClaimSum ?? 0);
+			var letzteRg = item.VorhandeneRechungen.OrderByDescending(r => r.ServiceInvoiceOid).FirstOrDefault();
 
-            if (item.NeueRechnung.ClaimSum == alterBetrag)
+			if (item.NeueRechnung.ClaimSum == letzteRg.ClaimSum)
 			{
 				diffRechnung = item.NeueRechnung;
 				diffRechnung.InvoiceBase.NeuErstellen = false;
@@ -107,30 +108,21 @@ namespace BeWo.Service.Plugins
 			}
 			else
             {
-				diffRechnung = new ServiceInvoiceDC();
-				diffRechnung.OriginalZurDifferenz = item.NeueRechnung;
-				diffRechnung.InvoiceBase = new InvoiceBaseDC();
-				CopyInvoiceBaseDC(item.NeueRechnung.InvoiceBase, diffRechnung);
+                diffRechnung = new ServiceInvoiceDC();
+                diffRechnung.OriginalZurDifferenz = item.NeueRechnung;
+                diffRechnung.InvoiceBase = new InvoiceBaseDC();
+                CopyInvoiceBaseDC(item.NeueRechnung.InvoiceBase, diffRechnung);
 
-				var newItem = new InvoiceItemDC();
-				newItem.ItemPeriodStart = item.NeueRechnung.InvoiceBase.AccountingPeriodStart;
-				newItem.ItemPeriodEnd = item.NeueRechnung.InvoiceBase.AccountingPeriodEnd;
-				newItem.UnitCount = 1;
-				newItem.AmountPerUnit = item.NeueRechnung.ClaimSum - alterBetrag;
-				newItem.AmountTotal = newItem.AmountPerUnit;
-				newItem.GrossAmountTotal = newItem.AmountTotal;
-				newItem.ItemDescription = String.Format("Rechnungsdifferenz zu Rechnung {0} in Höhe von {1:c}", item.VorhandeneRechungen[0].InvoiceBase.InvoiceNumber, alterBetrag);
-				diffRechnung.InvoiceBase.Hinweise = String.Format("Rechnungsdifferenz zu Rechnung {0} in Höhe von {1:c}", item.VorhandeneRechungen[0].InvoiceBase.InvoiceNumber, alterBetrag);
+                ServiceInvoice counterInvoice = new ServiceInvoice();
+				var serviceInvoice = DAOFactory.SearchDAO.GetServiceInvoiceByInvoiceBaseOid(letzteRg.InvoiceBase.InvoiceBaseOid.Value);
 
-				var newSip = new ServiceInvoicePeriodDC();
-				newSip.Claim = newItem.AmountTotal;
-				newSip.Start = item.NeueRechnung.InvoiceBase.AccountingPeriodStart;
-				newSip.End = item.NeueRechnung.InvoiceBase.AccountingPeriodEnd;
-				diffRechnung.ServiceInvoicePeriods = new List<ServiceInvoicePeriodDC>();
-				diffRechnung.ServiceInvoicePeriods.Add(newSip);
-				newSip.InvoiceItems = new List<InvoiceItemDC>();
-				newSip.InvoiceItems.Add(newItem);
-            }
+				CopyServiceInvoice(serviceInvoice, counterInvoice);
+				SetzeStornoInfos(counterInvoice);
+				SetzeRechnungspositionenServiceInvoice(diffRechnung, counterInvoice, item);
+				
+				diffRechnung.InvoiceBase.NeuErstellen = true;
+				diffRechnung.InvoiceBase.Hinweise = String.Format("Rechnungsdifferenz zu Rechnung {0} in Höhe von {1:c}", letzteRg.InvoiceBase.InvoiceNumber, letzteRg.InvoiceBase.TotalAmount.Value);
+			}
 			return diffRechnung;
         }
 
@@ -153,30 +145,33 @@ namespace BeWo.Service.Plugins
 						var siAlt = DAOFactory.SearchDAO.GetServiceInvoiceByInvoiceBaseOid(i2.Oid.Value);
 						var siDCAlt = MapperFactory.ServiceInvoiceDC_ServiceInvoice.MapToNewDC(siAlt);
 
-						//InvoiceItems vergleichen?
-						//foreach (var sip in si.ServiceInvoicePeriods)
-						//{
-						//	foreach (var ii in sip.InvoiceItems)
-						//	{
-						//		typNeu = ii.ItemDescription;
-						//	}
-						//}
-
-						//foreach (var sip in siAlt.ServiceInvoicePeriodList)
-						//{
-						//	foreach (var ii in sip.InvoiceItemList)
-						//	{
-						//		typAlt = ii.ItemDescription;
-						//	}
-						//}
-
-						//if (typAlt == typNeu)
-						//{
-						//	exist = true;
-						//}
-
 						checkResult.VorhandeneRechungen.Add(siDCAlt);
 					}
+					else // Sammelrechnung
+                    {
+						if (i2.RecipientCostBearerOid == invoices[0].InvoiceBase.RecipientCostBearerOid)
+						{
+							var siAlt = DAOFactory.SearchDAO.GetServiceInvoiceByInvoiceBaseOid(i2.Oid.Value);
+							var siDCAlt = MapperFactory.ServiceInvoiceDC_ServiceInvoice.MapToNewDC(siAlt);
+							if (siAlt.ServiceInvoicePeriodList != null && siAlt.ServiceInvoicePeriodList.Count > 0)
+							{
+								foreach (var i in invoices)
+								{
+									if (i.ServiceInvoicePeriods != null && i.ServiceInvoicePeriods.Count > 0)
+									{
+										foreach (var sip in siDCAlt.ServiceInvoicePeriods)
+										{
+											if (sip.Customer != null && i.ServiceInvoicePeriods.Any(s => s.Customer.CustomerOid == sip.Customer.CustomerOid))
+											{
+												checkResult.VorhandeneRechungen.Add(siDCAlt);
+												break;
+											}
+										}
+									}
+								}
+							}
+						}
+					}
                 }  
             }
             return result;
@@ -230,7 +225,6 @@ namespace BeWo.Service.Plugins
 			return MapperFactory.InvoiceBaseDC_InvoiceBase.MapToNewDCs(list);
 		}
 
-
 		public virtual void DeactivateInvoiceBases(List<InvoiceBaseDC> invoices)
 	    {
 	        ServiceLogic.SetActivationType<InvoiceBase>(invoices.ToDictionary(i => i.InvoiceBaseOid.Value, i => i.InvoiceBaseVersion.Value), ActivationTypeId.Deleted);
@@ -276,7 +270,6 @@ namespace BeWo.Service.Plugins
 		public virtual ServiceInvoice ErstelleStornoRechnung(InvoiceBaseDC ibdc)
 	    {
 			ServiceInvoice newInvoice = new ServiceInvoice();
-
 			var serviceInvoice = DAOFactory.SearchDAO.GetServiceInvoiceByInvoiceBaseOid(ibdc.InvoiceBaseOid.Value);
 
 			CopyServiceInvoice(serviceInvoice, newInvoice);
@@ -364,7 +357,6 @@ namespace BeWo.Service.Plugins
 	        copyInvoice.AmountAdvancePayments = existingInvoice.AmountAdvancePayments;
 	        copyInvoice.AmountEquityContribution = existingInvoice.AmountEquityContribution;
 	        copyInvoice.ServiceUnitOid = existingInvoice.ServiceUnitOid;
-			
 
 			CopyInvoiceBase(existingInvoice.InvoiceBase, copyInvoice.InvoiceBase);
 
@@ -575,7 +567,52 @@ namespace BeWo.Service.Plugins
             copyItem.ServiceRecord = existingItem.ServiceRecord;
         }
 
-        public virtual Settlement2DC ErstelleDifferenzSpitzabrechnung(Settlement2DC neueRechnung, Settlement2DC letzteRechnung)
+		private void SetzeRechnungspositionenServiceInvoice(ServiceInvoiceDC diffRechnung, ServiceInvoice counterInvoice, DifferenzRechnungCheck item)
+		{
+			var siDCAlt = MapperFactory.ServiceInvoiceDC_ServiceInvoice.MapToNewDC(counterInvoice);
+			if (siDCAlt.ServiceInvoicePeriods != null && siDCAlt.ServiceInvoicePeriods.Count > 0)
+			{
+				diffRechnung.ServiceInvoicePeriods = siDCAlt.ServiceInvoicePeriods;
+			}
+
+			if (item.NeueRechnung.ServiceInvoicePeriods != null && item.NeueRechnung.ServiceInvoicePeriods.Count > 0)
+			{
+				if (diffRechnung.ServiceInvoicePeriods == null)
+				{
+					diffRechnung.ServiceInvoicePeriods = item.NeueRechnung.ServiceInvoicePeriods;
+				}
+				else
+				{
+					foreach (var NewSip in item.NeueRechnung.ServiceInvoicePeriods)
+					{
+						if (NewSip.InvoiceItems != null && NewSip.InvoiceItems.Count > 0)
+						{
+							if (NewSip.Customer != null && diffRechnung.ServiceInvoicePeriods.Any(s => s.Customer.CustomerOid == NewSip.Customer.CustomerOid) &&
+							NewSip.SupportConceptApprovalPeriod != null && NewSip.SupportConceptApprovalPeriod.SupportConceptApprovalPeriodOid.HasValue
+							&& diffRechnung.ServiceInvoicePeriods.Any(s => s.SupportConceptApprovalPeriod.SupportConceptApprovalPeriodOid.HasValue
+							&& s.SupportConceptApprovalPeriod.SupportConceptApprovalPeriodOid.Value == NewSip.SupportConceptApprovalPeriod.SupportConceptApprovalPeriodOid.Value))
+							{
+								var ip = diffRechnung.ServiceInvoicePeriods.Where(s => s.SupportConceptApprovalPeriod.SupportConceptApprovalPeriodOid.Value == NewSip.SupportConceptApprovalPeriod.SupportConceptApprovalPeriodOid.Value).First();
+								if (ip.InvoiceItems != null && ip.InvoiceItems.Count > 0)
+								{
+									ip.Claim += NewSip.Claim;
+									foreach (var ii in NewSip.InvoiceItems)
+									{
+										ip.InvoiceItems.Add(ii);
+									}
+								}
+							}
+							else
+							{
+								diffRechnung.ServiceInvoicePeriods.Add(NewSip);
+							}
+						}
+					}
+				}
+			}
+		}
+
+		public virtual Settlement2DC ErstelleDifferenzSpitzabrechnung(Settlement2DC neueRechnung, Settlement2DC letzteRechnung)
         {
 			var diff = neueRechnung.Claim - letzteRechnung.Claim;
 			var ii = new InvoiceItemDC();