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

# Error Reference

> HTTP error formats and common causes.

All error responses follow this shape:

```json theme={null}
{
  "success": false,
  "error": "human-readable message"
}
```

| HTTP Status | Meaning        | Common cause                                            |
| ----------- | -------------- | ------------------------------------------------------- |
| `400`       | Bad request    | Missing or invalid field in request body                |
| `401`       | Unauthorized   | Missing, expired, or malformed access token             |
| `403`       | Forbidden      | Token does not have permission for this action          |
| `404`       | Not found      | Resource ID does not exist                              |
| `409`       | Conflict       | e.g. refund already issued for this intent              |
| `422`       | Unprocessable  | e.g. no customer wallet on file to refund               |
| `500`       | Platform error | Transient server fault — retry with exponential backoff |

> **On `5xx` errors:** implement retry logic with exponential backoff and jitter. Do not retry `4xx` errors without first fixing the request.

***