---
title: "API errors"
description: "Understand SumUp API error responses, HTTP status codes, and Problem Details."
image: "https://developer.sumup.com/og/index.png"
---

> Documentation Index
> Fetch the complete documentation index at: https://developer.sumup.com/llms.txt
> Use this file to discover all available pages before exploring further.

# API errors

SumUp APIs use HTTP status codes to indicate whether a request succeeded. Each operation's [API reference](/api/) documents its responses and response schemas.

## Problem Details

Newer APIs use [Problem Details (RFC 9457)](https://www.rfc-editor.org/rfc/rfc9457.html) for error responses. Some APIs support both `application/problem+json` and `application/json` for backwards compatibility.

If you do not use a SumUp SDK, send the following header to request the Problem Details format where it is supported:

```http
Accept: application/problem+json, application/json
```

A Problem Details response can include the following fields:

- `type`: a URI identifying the problem type.
- `title`: a short summary of the problem.
- `status`: the HTTP status code.
- `detail`: an explanation specific to this occurrence.
- `instance`: a URI identifying the specific occurrence.

Additional fields may be present. See the [Problem schema](/api/schemas/Problem/) for the complete definition.

```json
{
  "type": "https://developer.sumup.com/problem/not-found",
  "title": "Requested resource couldn't be found.",
  "status": 404,
  "detail": "The requested resource doesn't exist or does not belong to you."
}
```

## HTTP status codes

| Status | Meaning                    | When it is returned                                                     |
| ------ | -------------------------- | ----------------------------------------------------------------------- |
| `200`  | OK                         | The request finished successfully.                                      |
| `400`  | Bad Request                | The payload is invalid, incomplete, or does not match the API contract. |
| `401`  | Unauthorized               | Authentication is missing or the credentials are invalid.               |
| `402`  | Request Failed             | The request format is valid, but it could not be completed.             |
| `403`  | Forbidden                  | The authenticated caller does not have permission for this operation.   |
| `404`  | Not Found                  | The requested endpoint or resource could not be located.                |
| `409`  | Conflict                   | The request conflicts with the current resource state.                  |
| `422`  | Unprocessable Entity       | The payload is syntactically valid, but semantic validation failed.     |
| `424`  | External Dependency Failed | A required upstream service failed, so the request could not finish.    |
| `429`  | Too Many Requests          | Rate limits were exceeded. Retry with exponential backoff.              |
| `5xx`  | Server Errors              | An issue occurred on SumUp's side.                                      |

Source: https://developer.sumup.com/tools/errors/index.mdx