diff --git a/backend/src/controllers/contract.controller.ts b/backend/src/controllers/contract.controller.ts
index 17fa3247..730b58c5 100644
--- a/backend/src/controllers/contract.controller.ts
+++ b/backend/src/controllers/contract.controller.ts
@@ -539,7 +539,7 @@ export async function getCockpit(req: AuthRequest, res: Response): Promise<void>
 export async function addSuccessorMeter(req: AuthRequest, res: Response): Promise<void> {
   try {
     const contractId = parseInt(req.params.id);
-    const { meterId, installedAt, finalReadingPrevious } = req.body;
+    const { meterId, installedAt, finalReadingPrevious, deactivatePredecessor } = req.body;
 
     const contract = await prisma.contract.findUnique({
       where: { id: contractId },
@@ -648,6 +648,15 @@ export async function addSuccessorMeter(req: AuthRequest, res: Response): Promis
       );
     }
 
+    // Alten Zähler deaktivieren (Default), sofern der Aufrufer das nicht
+    // explizit auf false setzt – ein-klick-fähiger Zählerwechsel.
+    if (predecessorMeterId && deactivatePredecessor !== false) {
+      await prisma.meter.update({
+        where: { id: predecessorMeterId },
+        data: { isActive: false },
+      });
+    }
+
     await logChange({
       req, action: 'CREATE', resourceType: 'ContractMeter',
       resourceId: contractMeter.id.toString(),
diff --git a/backend/src/services/customer.service.ts b/backend/src/services/customer.service.ts
index 5868e7f4..918f02d5 100644
--- a/backend/src/services/customer.service.ts
+++ b/backend/src/services/customer.service.ts
@@ -488,6 +488,10 @@ export async function createMeter(
       predecessorMeterId: number;
       installedAt?: string;
       finalReadingPrevious?: number;
+      // Default true im UI: alter Zähler wird nach dem Wechsel auf
+      // isActive=false gesetzt. Kann ausgeschaltet werden, wenn der alte
+      // Zähler aus irgendeinem Grund noch aktiv bleiben soll.
+      deactivatePredecessor?: boolean;
     };
   }
 ) {
@@ -622,6 +626,16 @@ export async function createMeter(
         data.successorOf.finalReadingPrevious,
       );
     }
+
+    // Alten Zähler deaktivieren (Default), sofern der Aufrufer das nicht
+    // explizit auf false setzt. Macht den typischen Zählerwechsel-Workflow
+    // ein-klick-fähig.
+    if (data.successorOf.deactivatePredecessor !== false) {
+      await prisma.meter.update({
+        where: { id: predecessor.id },
+        data: { isActive: false },
+      });
+    }
   }
 
   return created;
diff --git a/frontend/src/pages/contracts/ContractDetail.tsx b/frontend/src/pages/contracts/ContractDetail.tsx
index 10fa9995..ed90726f 100644
--- a/frontend/src/pages/contracts/ContractDetail.tsx
+++ b/frontend/src/pages/contracts/ContractDetail.tsx
@@ -361,6 +361,7 @@ function SuccessorMeterButton({
   const [selectedMeterId, setSelectedMeterId] = useState('');
   const [installedAt, setInstalledAt] = useState(new Date().toISOString().split('T')[0]);
   const [finalReading, setFinalReading] = useState('');
+  const [deactivatePredecessor, setDeactivatePredecessor] = useState(true);
   const queryClient = useQueryClient();
 
   const { data: metersData } = useQuery({
@@ -370,13 +371,14 @@ function SuccessorMeterButton({
   });
 
   const addMutation = useMutation({
-    mutationFn: (data: { meterId: number; installedAt?: string; finalReadingPrevious?: number }) =>
+    mutationFn: (data: { meterId: number; installedAt?: string; finalReadingPrevious?: number; deactivatePredecessor?: boolean }) =>
       contractApi.addSuccessorMeter(contractId, data),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['contract'] });
       setShowForm(false);
       setSelectedMeterId('');
       setFinalReading('');
+      setDeactivatePredecessor(true);
     },
   });
 
@@ -451,6 +453,15 @@ function SuccessorMeterButton({
           erfasst und fließt damit in die Verbrauchsberechnung ein.
         </p>
       )}
+      <label className="flex items-center gap-2 mt-3 text-sm">
+        <input
+          type="checkbox"
+          checked={deactivatePredecessor}
+          onChange={(e) => setDeactivatePredecessor(e.target.checked)}
+          className="rounded"
+        />
+        Alten Zähler deaktivieren
+      </label>
       <div className="flex gap-2 mt-3">
         <Button
           size="sm"
@@ -458,6 +469,7 @@ function SuccessorMeterButton({
             meterId: parseInt(selectedMeterId),
             installedAt,
             finalReadingPrevious: finalReading ? parseFloat(finalReading) : undefined,
+            deactivatePredecessor,
           })}
           disabled={!selectedMeterId || addMutation.isPending}
         >
diff --git a/frontend/src/pages/customers/CustomerDetail.tsx b/frontend/src/pages/customers/CustomerDetail.tsx
index f2112dd2..85524f4a 100644
--- a/frontend/src/pages/customers/CustomerDetail.tsx
+++ b/frontend/src/pages/customers/CustomerDetail.tsx
@@ -2854,6 +2854,7 @@ function MeterModal({
     predecessorMeterId: '',
     installedAt: today,
     finalReadingPrevious: '',
+    deactivatePredecessor: true,
   });
 
   const [formData, setFormData] = useState(getInitialFormData);
@@ -2919,6 +2920,7 @@ function MeterModal({
         finalReadingPrevious: formData.finalReadingPrevious
           ? parseFloat(formData.finalReadingPrevious)
           : undefined,
+        deactivatePredecessor: formData.deactivatePredecessor,
       };
     }
     if (isEditing) {
@@ -3037,6 +3039,15 @@ function MeterModal({
                   onChange={(e) => setFormData({ ...formData, finalReadingPrevious: e.target.value })}
                   placeholder="Optional"
                 />
+                <label className="flex items-center gap-2 text-sm">
+                  <input
+                    type="checkbox"
+                    checked={formData.deactivatePredecessor}
+                    onChange={(e) => setFormData({ ...formData, deactivatePredecessor: e.target.checked })}
+                    className="rounded"
+                  />
+                  Alten Zähler deaktivieren
+                </label>
                 <p className="text-xs text-blue-700">
                   Typ, Adresse und Tarifmodell werden vom Vorgänger übernommen. Alle Verträge,
                   die den Vorgänger-Zähler verwenden, werden automatisch auf diesen neuen Zähler
diff --git a/frontend/src/services/api.ts b/frontend/src/services/api.ts
index 16f543f9..0f8db684 100644
--- a/frontend/src/services/api.ts
+++ b/frontend/src/services/api.ts
@@ -837,7 +837,7 @@ export const contractApi = {
     return res.data;
   },
   // Folgezähler
-  addSuccessorMeter: async (contractId: number, data: { meterId: number; installedAt?: string; finalReadingPrevious?: number }) => {
+  addSuccessorMeter: async (contractId: number, data: { meterId: number; installedAt?: string; finalReadingPrevious?: number; deactivatePredecessor?: boolean }) => {
     const res = await api.post<ApiResponse<any>>(`/contracts/${contractId}/successor-meter`, data);
     return res.data;
   },