# Error codes (API)


When request processing fails, the API returns **HTTP 400** (or another method-specific error code) and JSON:

```json
{
  "error_code": 2
}
```

The `error_code` field is an integer. Meaning and actions are in the table below.

> Payment declines on the bank/processing side (`status_code` in callbacks) are in [Error codes (declines)](./decline-error-codes.md).

## `error_code` reference

| Code | Meaning | Action |
| --- | --- | --- |
| `1` | General error without details. | Contact 1Payment support with `order_id` / `user_data` and request time. |
| `2` | Invalid `sign` signature. | Verify the **project key** (not global), method prefix, A→Z parameter order, MD5, lowercase (hex). Check [API request format](./init-request.md) or the signature widget on the method page. If still failing, send support the raw string before MD5. |
| `3` | Method unavailable. | Check the URL and method name; confirm with your manager that the method is enabled on the project. |
| `4` | Partner not found. | Verify `partner_id` in the dashboard / with your manager. |
| `5` | Project not found. | Verify `project_id` and its link to `partner_id`. |
| `6` | **Payment acceptance** method not enabled on the project. | Check `payment_type` and channel agreement (card, SBP, SberPay). See [Payment types](./payment-types.md). |
| `7` | **Payout** method not enabled on the project. | Check payout type and project settings. See [Payout types](./payout-types.md). |
| `8` | `user_data` error. | Send a non-empty string up to 255 characters; value must be **unique** within `partner_id` (UUID recommended). Do not reuse an ID from an existing payment. |
| `9` | Insufficient payout balance. | Top up the payout balance or reduce the amount; confirm limits with your manager. |
| `10` | Transaction not found. | Check `order_id` / `user_data` and `project_id`; ensure the payment was created in this project. |
| `11` | Payment from this source unavailable. | Check `shop_url`, domain, and project settings; submit the site for review via your manager if needed. |

## Related sections

- [Error codes (declines)](./decline-error-codes.md)
- [API request format](./init-request.md)