diff --git a/frontend/src/utils/index.ts b/frontend/src/utils/index.ts
index f5a45b7f11337b9db62db3be61b757b7e99500a8..528734dd17370f1f3149f061a59a1a15d5a6e631 100644
--- a/frontend/src/utils/index.ts
+++ b/frontend/src/utils/index.ts
@@ -43,8 +43,14 @@ export function submitJsonOpts(method: string, data: object): RequestInit {
   }
 }
 
-export function isValidFnr(data: string | undefined): boolean | string {
-  if (data === undefined) {
+export function isValidFnr(
+  data: string | undefined,
+  allowEmpty = false
+): boolean | string {
+  if (!data) {
+    if (allowEmpty) {
+      return true
+    }
     return i18n.t<string>('common:validation.invalidIdNumber').toString()
   }
   const valid = validator.idnr(data as string).status === 'valid'