diff --git a/backend/db/migrations/0036_allowed_contracttypes.sql b/backend/db/migrations/0036_allowed_contracttypes.sql
new file mode 100644
index 0000000..3254325
--- /dev/null
+++ b/backend/db/migrations/0036_allowed_contracttypes.sql
@@ -0,0 +1 @@
+ALTER TABLE "contracts" ADD COLUMN "allowedContracttypes" jsonb DEFAULT '[]'::jsonb NOT NULL;
diff --git a/backend/db/migrations/meta/_journal.json b/backend/db/migrations/meta/_journal.json
index 8c4e6d3..5279f08 100644
--- a/backend/db/migrations/meta/_journal.json
+++ b/backend/db/migrations/meta/_journal.json
@@ -246,6 +246,13 @@
       "when": 1778191200000,
       "tag": "0035_contract_history",
       "breakpoints": true
+    },
+    {
+      "idx": 35,
+      "version": "7",
+      "when": 1778194800000,
+      "tag": "0036_allowed_contracttypes",
+      "breakpoints": true
     }
   ]
 }
diff --git a/backend/db/schema/contracts.ts b/backend/db/schema/contracts.ts
index 2a32e67..c9dc973 100644
--- a/backend/db/schema/contracts.ts
+++ b/backend/db/schema/contracts.ts
@@ -52,6 +52,7 @@ export const contracts = pgTable(
         contracttype: bigint("contracttype", { mode: "number" }).references(
             () => contracttypes.id
         ),
+        allowedContracttypes: jsonb("allowedContracttypes").notNull().default([]),
 
         bankingIban: text("bankingIban"),
         bankingBIC: text("bankingBIC"),
diff --git a/backend/src/routes/portal/contracts.ts b/backend/src/routes/portal/contracts.ts
index 2a10745..d049dd6 100644
--- a/backend/src/routes/portal/contracts.ts
+++ b/backend/src/routes/portal/contracts.ts
@@ -32,6 +32,7 @@ async function getPortalContract(server: FastifyInstance, req: any, contractId:
             tenant: contracts.tenant,
             customer: contracts.customer,
             contracttype: contracts.contracttype,
+            allowedContracttypes: contracts.allowedContracttypes,
             archived: contracts.archived,
         })
         .from(contracts)
@@ -121,6 +122,14 @@ export default async function portalContractRoutes(server: FastifyInstance) {
             return reply.code(400).send({ error: "Ungültiger Vertragstyp" })
         }
 
+        const allowedContracttypes = Array.isArray(contract.allowedContracttypes)
+            ? contract.allowedContracttypes.map((id) => Number(id)).filter((id) => Number.isInteger(id))
+            : []
+
+        if (!allowedContracttypes.includes(requestedContracttype.id)) {
+            return reply.code(400).send({ error: "Dieser Vertragstyp steht für diesen Vertrag nicht zur Auswahl" })
+        }
+
         const [currentContracttype] = contract.contracttype
             ? await server.db
                 .select({
diff --git a/frontend/pages/customer-portal.vue b/frontend/pages/customer-portal.vue
index 263bf23..e5a0008 100644
--- a/frontend/pages/customer-portal.vue
+++ b/frontend/pages/customer-portal.vue
@@ -165,9 +165,27 @@ function getContactLabel(contact: any) {
   return contact.fullName || [contact.firstName, contact.lastName].filter(Boolean).join(" ") || contact.email || contact.id || "-"
 }
 
+function getAllowedContracttypeIds(contract: any) {
+  if (!Array.isArray(contract?.allowedContracttypes)) return []
+  return contract.allowedContracttypes.map((id: any) => Number(id)).filter((id: number) => Number.isInteger(id))
+}
+
+function getAllowedContracttypes(contract: any) {
+  const allowedIds = getAllowedContracttypeIds(contract)
+  return contracttypes.value.filter((item: any) => allowedIds.includes(Number(item.id)))
+}
+
+const selectedContractAllowedContracttypes = computed(() => {
+  if (!selectedContract.value) return []
+  return getAllowedContracttypes(selectedContract.value)
+})
+
 function openContractChangeRequest(contract: any) {
+  const allowedTypes = getAllowedContracttypes(contract)
   selectedContract.value = contract
-  contractChangeForm.contracttype = contract.contracttype?.id || null
+  contractChangeForm.contracttype = allowedTypes.some((item: any) => item.id === contract.contracttype?.id)
+      ? contract.contracttype.id
+      : allowedTypes[0]?.id || null
   contractChangeForm.message = ""
   contractChangeModalOpen.value = true
 }
@@ -589,6 +607,7 @@ onMounted(async () => {
                         variant="soft"
                         icon="i-heroicons-pencil-square"
                         class="justify-center"
+                        :disabled="getAllowedContracttypes(contract).length === 0"
                         @click="openContractChangeRequest(contract)"
                       >
                         Änderung anfragen
@@ -611,6 +630,22 @@ onMounted(async () => {
                           {{ contract.contracttype?.name || "Nicht hinterlegt" }}
                         </p>
                       </div>
+                      <div class="rounded-xl bg-white p-3">
+                        <p class="text-xs uppercase tracking-wide text-neutral-400">Änderung möglich zu</p>
+                        <div v-if="getAllowedContracttypes(contract).length" class="mt-2 flex flex-wrap gap-2">
+                          <UBadge
+                            v-for="type in getAllowedContracttypes(contract)"
+                            :key="type.id"
+                            color="primary"
+                            variant="soft"
+                          >
+                            {{ type.name }}
+                          </UBadge>
+                        </div>
+                        <p v-else class="mt-1 text-sm font-medium text-neutral-900">
+                          Keine Änderungstypen freigegeben
+                        </p>
+                      </div>
                       <div class="rounded-xl bg-white p-3">
                         <p class="text-xs uppercase tracking-wide text-neutral-400">Ansprechpartner</p>
                         <p class="mt-1 text-sm font-medium text-neutral-900">
@@ -751,12 +786,15 @@ onMounted(async () => {
               <label class="mb-1 block text-sm font-medium text-neutral-700">Gewünschter Vertragstyp</label>
               <USelectMenu
                 v-model="contractChangeForm.contracttype"
-                :items="contracttypes"
+                :items="selectedContractAllowedContracttypes"
                 value-key="id"
                 label-key="name"
                 class="w-full"
                 placeholder="Vertragstyp auswählen"
               />
+              <p v-if="!selectedContractAllowedContracttypes.length" class="mt-2 text-sm text-neutral-500">
+                Für diesen Vertrag sind aktuell keine Änderungstypen freigegeben.
+              </p>
             </div>
             <div>
               <label class="mb-1 block text-sm font-medium text-neutral-700">Nachricht optional</label>
diff --git a/frontend/stores/data.js b/frontend/stores/data.js
index 6abe4db..03d2493 100644
--- a/frontend/stores/data.js
+++ b/frontend/stores/data.js
@@ -853,6 +853,15 @@ export const useDataStore = defineStore('data', () => {
                         item.billingInterval = selectedContractType.billingInterval || null
                     },
                     inputColumn: "Allgemeines"
+                },{
+                    key: "allowedContracttypes",
+                    label: "Vertragstypen für Änderungsanfragen",
+                    inputType: "select",
+                    selectDataType: "contracttypes",
+                    selectOptionAttribute: "name",
+                    selectSearchAttributes: ["name"],
+                    selectMultiple: true,
+                    inputColumn: "Allgemeines"
                 },{
                     key: "active",
                     label: "Aktiv",