diff --git a/Dakota/Models/Infos/InfoParameterInvoiceItem.cs b/Dakota/Models/Infos/InfoParameterInvoiceItem.cs
index a21129002..9b96aa75d 100644
--- a/Dakota/Models/Infos/InfoParameterInvoiceItem.cs
+++ b/Dakota/Models/Infos/InfoParameterInvoiceItem.cs
@@ -1,5 +1,6 @@
 using BeWo.Data.Models;
 using BS.Shared.DataContracts;
+using BS.Shared.Exceptions;
 using Dakota.Models.Schlüssels;
 using System;
 using System.Collections.Generic;
@@ -33,7 +34,7 @@ namespace Dakota.Models.Infos
             AddressInformation = addressInformation;
 
             // Todo: Valid prüfen
-            Abrechnungsposition = invoiceItem.UnitDescription?.Substring(6) ?? "TODO";
+            Abrechnungsposition = invoiceItem.UnitDescription.Substring(6);
         }
     }
 }
diff --git a/Data/Entities/InvoiceBase.cs b/Data/Entities/InvoiceBase.cs
index 18cbf2f7f..cd108fc75 100644
--- a/Data/Entities/InvoiceBase.cs
+++ b/Data/Entities/InvoiceBase.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-
+using System.Linq;
 using BS.Shared;
 using BS.Shared.Interface;
 
@@ -830,5 +830,6 @@ namespace BeWo.Data.Entities
 		public virtual string SenderStreet => SenderAddress?.Street;
 		public virtual string SenderTown => SenderAddress?.Town;
         public virtual string SenderPostCode => SenderAddress?.PostalCode;
-    }
+        public virtual IList<IInvoiceItem> IInvoiceItems => InvoiceItems.Select(x => x as IInvoiceItem).ToList(); 
+	}
 }
\ No newline at end of file
diff --git a/Data/Entities/InvoiceItem.cs b/Data/Entities/InvoiceItem.cs
index eee763828..56bce4e01 100644
--- a/Data/Entities/InvoiceItem.cs
+++ b/Data/Entities/InvoiceItem.cs
@@ -2,11 +2,12 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using BS.Shared;
+using BS.Shared.Interface;
 
 namespace BeWo.Data.Entities
 {
     [DebuggerDisplay("{ItemDescription}: {AmountPerUnit} x {UnitCount} = {AmountTotal}")]
-    public class InvoiceItem : BeWoEntityBase
+    public class InvoiceItem : BeWoEntityBase, IInvoiceItem
     {
         public static string PropertyName_AmountPerUnit = "AmountPerUnit";
 
diff --git a/Shared/Core/ValidatorExtended.cs b/Shared/Core/ValidatorExtended.cs
index 25f3f0ccd..7114fa30f 100644
--- a/Shared/Core/ValidatorExtended.cs
+++ b/Shared/Core/ValidatorExtended.cs
@@ -21,6 +21,8 @@ namespace BS.Shared.Core
 				error = "Keine Rechnungen gefunden";
 			else if (!AreAllAddressSame(invoiceBases))
 				error = "Unterschiedliche Rechnungspositionen";
+			else if (GetInvalidUnitDescription(invoiceBases) is IInvoiceItem invalid)
+				error = $"Ungültige Rechnungsposition: {invalid.ItemDescription}:{invalid.UnitDescription}";
 
 			if(error is string)
 				throw new GkvException(error, "Validierung");
@@ -42,5 +44,21 @@ namespace BS.Shared.Core
 
 		public static bool AreAllAddressSame(IEnumerable<IInvoiceBase> invoiceBases)
 			=> invoiceBases.Select(x => x.SenderAddressToString()).AreAllTheSame();
+
+		public static IInvoiceItem GetInvalidUnitDescription(IEnumerable<IInvoiceBase> invoiceBases){
+			foreach(var invoiceBase in invoiceBases)
+			{
+				foreach (var invoiceitem in invoiceBase.IInvoiceItems)
+				{
+					// GPos. 123456
+					// 0123456
+					var desc = invoiceitem.UnitDescription;
+					if (desc.Length < 8)
+						return invoiceitem;
+				}
+			}
+
+			return null;
+		}
 	}
 }
diff --git a/Shared/DataContracts/InvoiceItemDC.cs b/Shared/DataContracts/InvoiceItemDC.cs
index 5b480256f..254c2123e 100644
--- a/Shared/DataContracts/InvoiceItemDC.cs
+++ b/Shared/DataContracts/InvoiceItemDC.cs
@@ -1,3 +1,4 @@
+using BS.Shared.Interface;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
diff --git a/Shared/Interface/IInvoiceBase.cs b/Shared/Interface/IInvoiceBase.cs
index 01d69f634..251f24e39 100644
--- a/Shared/Interface/IInvoiceBase.cs
+++ b/Shared/Interface/IInvoiceBase.cs
@@ -11,5 +11,6 @@ namespace BS.Shared.Interface
 		string SenderStreet { get; }
 		string SenderTown { get; }
 		string SenderPostCode { get; }
+		IList<IInvoiceItem> IInvoiceItems { get; }
 	}
 }
diff --git a/Shared/Interface/IInvoiceItem.cs b/Shared/Interface/IInvoiceItem.cs
new file mode 100644
index 000000000..f9e150a90
--- /dev/null
+++ b/Shared/Interface/IInvoiceItem.cs
@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace BS.Shared.Interface
+{
+	public interface IInvoiceItem
+	{
+		string UnitDescription { get; }
+		string ItemDescription { get; }
+	}
+}
diff --git a/Shared/Shared.csproj b/Shared/Shared.csproj
index b031cc5e9..d0fefee7c 100644
--- a/Shared/Shared.csproj
+++ b/Shared/Shared.csproj
@@ -385,6 +385,7 @@
     <Compile Include="Interface\IGkvAbrechnung.cs" />
     <Compile Include="Interface\IGkvTransferProtokoll.cs" />
     <Compile Include="Interface\IInvoiceBase.cs" />
+    <Compile Include="Interface\IInvoiceItem.cs" />
     <Compile Include="Packet.cs" />
     <Compile Include="ReportRequests\AbstractReportRequest.cs" />
     <Compile Include="ReportRequests\GkvAbrechnungReportRequest.cs" />