# Error codes

The following table lists the error codes that the callbacks may return.

| **Code** | **Constant** | **Description** |
| --- | --- | --- |
| `1001` | `MPPErrorParamIllegal` | Invalid or illegal parameter. |
| `1002` | `MPPErrorInvalidNetwork` | Network is unavailable. |
| `1003` | `MPPErrorSystemError` | Internal system error. |
| `1004` | `MPPErrorUserCancel` | User canceled the operation. |
| `2001` | `MPPErrorPayFail` | Payment failed. |

> **Note**: These predefined codes must be used as the values for `NSError.code`. Defining custom error codes is not supported.