diff --git a/src/services/idnot/index.ts b/src/services/idnot/index.ts
index 537bf28..9ca3f43 100644
--- a/src/services/idnot/index.ts
+++ b/src/services/idnot/index.ts
@@ -1,5 +1,6 @@
 import fetch from 'node-fetch';
 import { IdNotUser, ECivility, EOfficeStatus, EIdnotRole } from '../../types';
+import { ValidationError, UnauthorizedError, ExternalServiceError } from '../../types/errors';
 
 export class IdNotService {
   static async exchangeCodeForTokens(code: string) {
@@ -31,7 +32,13 @@ export class IdNotService {
     });
 
     if (!response.ok) {
-      throw new Error(`Token exchange failed: ${response.status} ${response.statusText}`);
+      if (response.status === 400) {
+        throw new ValidationError('Invalid authorization code received from IdNot');
+      }
+      if (response.status === 401) {
+        throw new UnauthorizedError('Invalid IdNot client credentials');
+      }
+      throw new ExternalServiceError('IdNot', `Token exchange failed: ${response.status} ${response.statusText}`);
     }
 
     return response.json();