diff --git a/BeWoPlanerMobil/Controllers/MainController.cs b/BeWoPlanerMobil/Controllers/MainController.cs
index 0494f2dfe..a862b29be 100644
--- a/BeWoPlanerMobil/Controllers/MainController.cs
+++ b/BeWoPlanerMobil/Controllers/MainController.cs
@@ -1510,20 +1510,32 @@ namespace BeWoPlanerMobil.Controllers
 
                 if(!Model.IsInEditingMode)
                 {
-                    var oidList = OperationsService.InsertNewServiceRecords(new List<ServiceRecordDC> { Model.NewServiceRecord });
-
-                    Model.LastCreatedServiceRecordOid = oidList[0];
-
-                    TempData[TempDataConstants.AfterInsertKey] = true;
-
-                    if (Model.IsAllowedToCreateSignature(Model.NewServiceRecord))
+                    var valRes = OperationsService.ValidateServiceRecord(Model.NewServiceRecord, null, 0, null, null);
+                    bool doppelt = false;
+                    if (valRes.Count > 0 && valRes.FirstOrDefault(v => v.ResultType == ServiceRecordValidationResult.DoppelterEintrag) != null)
                     {
-                        if (Model.NewServiceRecord.CostBearer != null && Model.ShowSignature && (Model.NewServiceRecord.ServiceDescription.Category.IsBillable || Model.NewServiceRecord.ServiceDescription.Category.BillableAmount > 0m || Model.NewServiceRecord.ServiceDescription.BillableAmount > 0m))
+                        doppelt = true;
+
+
+                    }
+                    if (!doppelt)
+                    {
+                        var oidList = OperationsService.InsertNewServiceRecords(new List<ServiceRecordDC> { Model.NewServiceRecord });
+
+                        Model.LastCreatedServiceRecordOid = oidList[0];
+
+
+                        if (Model.IsAllowedToCreateSignature(Model.NewServiceRecord))
                         {
-                            TempData[TempDataConstants.ShowSignatureSuggestionPopup] = true;
+                            if (Model.NewServiceRecord.CostBearer != null && Model.ShowSignature && (Model.NewServiceRecord.ServiceDescription.Category.IsBillable || Model.NewServiceRecord.ServiceDescription.Category.BillableAmount > 0m || Model.NewServiceRecord.ServiceDescription.BillableAmount > 0m))
+                            {
+                                TempData[TempDataConstants.ShowSignatureSuggestionPopup] = true;
+                            }
                         }
                     }
-                    if(appointmentPrototype is object)
+                    TempData[TempDataConstants.AfterInsertKey] = true;
+
+                    if (appointmentPrototype is object)
                     {
                         var isRecurring = !(appointmentPrototype.RecurrenceInfo is null);
 
diff --git a/Service/Plugins/ServiceRecordValidator.cs b/Service/Plugins/ServiceRecordValidator.cs
index a675a2e62..9b00b6b33 100644
--- a/Service/Plugins/ServiceRecordValidator.cs
+++ b/Service/Plugins/ServiceRecordValidator.cs
@@ -226,7 +226,7 @@ namespace BeWo.Service.Plugins
 			return result;
 		}
 
-		public virtual List<ServiceRecordValidationResultDC> ValidateServiceRecord(ServiceRecordDC newServiceRecord, SupportConceptStatisticsDC statistics, int maxDaysEditServiceRecordsAllowed, IList<long> employeeOids, IList<long> cb2scOids)
+		public virtual List<ServiceRecordValidationResultDC> ValidateServiceRecord(ServiceRecordDC newServiceRecord, SupportConceptStatisticsDC statisticsXX, int maxDaysEditServiceRecordsAllowed, IList<long> employeeOids, IList<long> cb2scOids)
 		{
 			var result = new List<ServiceRecordValidationResultDC>();
             
@@ -1126,6 +1126,19 @@ namespace BeWo.Service.Plugins
 						rdc.EmployeeName = String.Format("{0} {1}", e.Person.FirstName, e.Person.LastName);
 					}
 
+					//CB, 19.03.2026: Prüfe ob ein Dopppler entstanden ist. Das ist mal im Mok passiert, konnte aber bisher nicht reproduziert werden.
+					if (overlappingRecord.Notice == newServiceRecord.Notice && 
+						overlappingRecord.Start == newServiceRecord.Start &&
+						overlappingRecord.End == newServiceRecord.End &&
+						overlappingRecord.InsTs > DateTime.Now.AddMinutes(-1) && 
+						overlappingRecord.IsCreatedInMobileClient && 
+						newServiceRecord.IsCreatedInMobileClient)
+                    {
+						if (overlappingRecord.CostBearer2SupportConcept != null && newServiceRecord.CostBearer2SupportConceptOid.HasValue && overlappingRecord.CostBearer2SupportConcept.Oid == newServiceRecord.CostBearer2SupportConceptOid.Value)
+                        {
+							rdc.ResultType = ServiceRecordValidationResult.DoppelterEintrag;
+                        }
+                    }
 					return rdc;
 				}
 			}
diff --git a/Shared/BeWoEntityEnums.cs b/Shared/BeWoEntityEnums.cs
index cef1066ee..7d55e38e1 100644
--- a/Shared/BeWoEntityEnums.cs
+++ b/Shared/BeWoEntityEnums.cs
@@ -953,7 +953,8 @@ namespace BS.Shared
         SettlementInvoiceAlreadyExisting = 6,
         FristAbgelaufen = 7,
         Custom = 8,
-        SignatureExists = 9
+        SignatureExists = 9,
+        DoppelterEintrag = 10 // Für Mok, da es da mal zu doppelten Einträgen gekommen ist.
     }
 
     public enum ViewDestination