# An Idempotency-Key header is required

> idempotency-key-required: HTTP 400. Send an Idempotency-Key header (a V4 UUID is a good choice) and reuse it on every retry.

Source: https://emailmovers.com/mydatahub/docs/errors/idempotency-key-required

`idempotency-key-required` is returned with HTTP status 400. Its type URI is `https://emailmovers.com/mydatahub/docs/errors/idempotency-key-required`.

## What it means

POST /v1/orders and POST /v1/contacts/enrich spend credits, so both need an Idempotency-Key header. Nothing was charged.

## What to do

Send an Idempotency-Key header (a V4 UUID is a good choice) and reuse it on every retry.

## Example

```json
{
  "type": "https://emailmovers.com/mydatahub/docs/errors/idempotency-key-required",
  "title": "An Idempotency-Key header is required",
  "status": 400,
  "code": "idempotency-key-required",
  "detail": "POST /v1/orders needs an Idempotency-Key header.",
  "next_step": "Send an Idempotency-Key header (a V4 UUID is a good choice) and reuse it on every retry."
}
```

## See also

- [Quotes and orders](https://emailmovers.com/mydatahub/docs/quotes-and-orders.md)
- [Spending safely](https://emailmovers.com/mydatahub/docs/spending-safely.md)

All problem types are listed on [Errors](https://emailmovers.com/mydatahub/docs/errors.md).