# `400` - Missing idempotency key

## Description

The request you are trying to execute requires an `idempotency-key` header in the request.

## How to fix

Provide an `idempotency-key` header in the request.

Further information can be found in the [concept documentation](/products/tol/concepts/api_concepts/idempotency).

## Example


```http
HTTP/1.1 400 Bad Request
content-length: 188
content-type: application/problem+json
date: Mon, 11 Oct 2021 10:42:01 GMT
upvest-request-id: e7378103-7d45-4052-a049-7c9ac88d041c

{
    "type": "https://docs.upvest.co/errors/missing_idempotency_key",
    "status": 400,
    "title": "Missing idempotency key",
    "request_id": "e7378103-7d45-4052-a049-7c9ac88d041c"
}
```