---
title: "Check NIF duplicate"
method: GET
path: "/api/clients/check-nif"
tags: ["Clients - Protected"]
---

# Check NIF duplicate

`GET /api/clients/check-nif`

Check if a NIF (Portuguese or foreign) is already linked to a client
in the same company. Matches against both Cliente.NIF and Cliente.foreign_NIF.

## Query parameters

- `nif` string, required — NIF (Portuguese 9-digit or foreign alphanumeric) to check
- `exclude_id` integer, nullable — Client ID to exclude (for updates)

## Headers

- `x-api-token` string, nullable

## Response `200`

Successful Response

- NifCheckResponse — NIF duplicate check response.
  - `exists` boolean, required
  - `client_id` integer, nullable
  - `client_name` string, nullable
  - `is_foreign` boolean

## Other responses

- `422` — Validation Error

---

[API](https://skmtc.dev/multigest/apis/multigest-protected-api.md) · [All operations](https://skmtc.dev/multigest/apis/multigest-protected-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/multigest/multigest-protected-api/revisions/4b44eb76b3ee/schema)