> For the complete documentation index, see [llms.txt](https://docs.ecommerce.seb.ee/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ecommerce.seb.ee/integration/merchant-api/response-handling/error-codes.md).

# Error Codes

When a request cannot be processed successfully, the API returns an appropriate HTTP status code together with an error code describing the specific reason for the failure. The following table lists the possible error responses and their meanings.

| HTTP Status               | Error Code                                                                                                                              | Description                                                                                                                                                    |
| ------------------------- | --------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `400` Bad Request         | `FORMAT_ERROR`                                                                                                                          | The request contains invalid, malformed, or missing required data.                                                                                             |
| `400` Bad Request         | `AMOUNT_EXCEEDED`                                                                                                                       | The requested refund amount exceeds the available refundable amount.                                                                                           |
| `401` Unauthorized        | `TOKEN_UNKNOWN`, `TOKEN_EXPIRED`                                                                                                        | Authentication failed because the access token is missing, invalid, or expired.                                                                                |
| `403` Forbidden           | `OPERATION_NOT_ALLOWED`                                                                                                                 | The requested operation is not permitted due to business rules or account restrictions.                                                                        |
| `403` Forbidden           | `PAYMENT_METHOD_INVALID`                                                                                                                | The selected payment method is not available for the shop                                                                                                      |
| `404` Not Found           | `RESOURCE_UNKNOWN`, `PAYMENT_UNKNOWN`, `SESSION_UNKNOWN`, `GATEWAY_TOKEN_UNKNOWN`, `REFUND_UNKNOWN`, `MERCHANT_UNKNOWN`, `SHOP_UNKNOWN` | The requested resource does not exist.                                                                                                                         |
| `409` Conflict            | `STATUS_INVALID`                                                                                                                        | The requested operation is not allowed in the current state of the resource. For example, attempting to capture a payment that has been refunded, or canceled. |
| `429` Too Many Requests   | `OPERATION_NOT_ALLOWED`                                                                                                                 | The request rate limit has been exceeded. Retry the request later.                                                                                             |
| `503` Service Unavailable | `INTERNAL_SERVER_ERROR`                                                                                                                 | The request could not be processed due to a temporary service interruption or internal system error.                                                           |


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