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

# DeclineCallback

The `DeclineCallback` API call is used to notify you of a failure in the Spark transaction process. It is typically triggered after a successful `/TriggerTransaction` response with a verdict of `Approved`, but when the flow subsequently fails for any reason before payment authorization.

This callback is essential for integrators to detect and gracefully handle cases where a session cannot proceed, such as when:

* The consumer did not present a payment card, and the terminal timed out.
* The consumer canceled the transaction on the Nayax Device.
* A failure occurred on the device during the card presentation.
* Other terminal-side errors that disrupt the flow.

In such cases, no payment authorization is granted, and the transaction flow is terminated. If appropriate, the integrator may choose to re-attempt the `/TriggerTransaction` method.

## Request

Spark sends a POST request to the `/spark/DeclineCallback` endpoint:

```json theme={null}
{
  "MachineId": 71234996,
  "HwSerial": "0434334921100366",
  "SparkTransactionId": "12c7cec2-c690-4425-9a1f-db0db60e2d8c",
  "Status": {
    "Verdict": "Declined",
    "ErrorCode": 44,
    "ErrorDescription": "Timeout on POS Device"
  }
}
```

### Request Parameters

The table below describes the parameters of the request:

<table>
  <thead>
    <tr>
      <th>
        Field
      </th>

      <th>
        Type
      </th>

      <th>
        Required
      </th>

      <th>
        Description
      </th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>
        `MachineId`
      </td>

      <td>
        Integer
      </td>

      <td>
        Yes
      </td>

      <td>
        The ID of the vending machine or terminal
      </td>
    </tr>

    <tr>
      <td>
        `HwSerial`
      </td>

      <td>
        String
      </td>

      <td>
        Yes
      </td>

      <td>
        Serial number of the hardware terminal
      </td>
    </tr>

    <tr>
      <td>
        `SparkTransactionId`
      </td>

      <td>
        String
      </td>

      <td>
        Yes
      </td>

      <td>
        The unique identifier of the failed Spark transaction
      </td>
    </tr>

    <tr>
      <td>
        `Status`
      </td>

      <td>
        Object
      </td>

      <td>
        Yes
      </td>

      <td>
        An object indicating decline details
      </td>
    </tr>

    <tr>
      <td>
        `Status.Verdict`
      </td>

      <td>
        String
      </td>

      <td>
        Yes
      </td>

      <td>
        Always "Declined"
      </td>
    </tr>

    <tr>
      <td>
        `Status.ErrorCode`
      </td>

      <td>
        Integer
      </td>

      <td>
        Yes
      </td>

      <td>
        Decline reason code

        * `44`: Timeout on POS Device
        * `45`: Cancelled on POS Device
        * `38`: Transaction Callback Failed
      </td>
    </tr>

    <tr>
      <td>
        `Status.ErrorDescription`
      </td>

      <td>
        String
      </td>

      <td>
        Yes
      </td>

      <td>
        Description of the decline reason
      </td>
    </tr>
  </tbody>
</table>

<Note>
  **Nayax Callback**

  This is a callback from Nayax, no response body is required. A simple 200 OK server acknowledgment is sufficient.
</Note>