diff --git a/docs/api/routes/supplier/delete.md b/docs/api/routes/supplier/delete.md
index 2352bd8..4973698 100644
--- a/docs/api/routes/supplier/delete.md
+++ b/docs/api/routes/supplier/delete.md
@@ -28,6 +28,7 @@ _No content_
 | 401 | Unauthorized — `{"error":"…"}` |
 | 403 | Not authorized — `{"error":"…"}` |
 | 404 | Supplier not found — `{"error":"…"}` |
+| 409 | Supplier in use — `{"error":"…"}` |
 
 ---
 
diff --git a/src/api/routes/entity.js b/src/api/routes/entity.js
index 8411213..e31bde8 100644
--- a/src/api/routes/entity.js
+++ b/src/api/routes/entity.js
@@ -19,6 +19,8 @@ function entityErrorStatus(error) {
     if (error.message === 'Name required') return 400;
     if (error.message === 'Number required') return 400;
     if (error.message === 'Number already in use') return 409;
+    if (error.message === 'Entity in use') return 409;
+    if (error.message === 'Supplier in use') return 409;
     if (error.message === 'Invalid customergroupId') return 400;
     if (error.message === 'Invalid role') return 400;
     return 500;
diff --git a/src/api/routes/supplier.js b/src/api/routes/supplier.js
index ba6bb8f..6203e46 100644
--- a/src/api/routes/supplier.js
+++ b/src/api/routes/supplier.js
@@ -17,6 +17,7 @@ function supplierErrorStatus(error) {
     if (error.message === 'Supplier not found') return 404;
     if (error.message === 'Supplier required') return 400;
     if (error.message === 'Name required') return 400;
+    if (error.message === 'Supplier in use') return 409;
     return 500;
 }
 
@@ -307,6 +308,12 @@ export function register(app, basePath = '') {
      *           application/json:
      *             schema:
      *               $ref: '#/components/schemas/Error'
+     *       409:
+     *         description: Supplier in use
+     *         content:
+     *           application/json:
+     *             schema:
+     *               $ref: '#/components/schemas/Error'
      */
     // #region PATCH /supplier/:id