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:

{
  "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:

Field	Type	Required	Description
`MachineId`	Integer	Yes	The ID of the vending machine or terminal
`HwSerial`	String	Yes	Serial number of the hardware terminal
`SparkTransactionId`	String	Yes	The unique identifier of the failed Spark transaction
`Status`	Object	Yes	An object indicating decline details
`Status.Verdict`	String	Yes	Always "Declined"
`Status.ErrorCode`	Integer	Yes	Decline reason code `44`: Timeout on POS Device `45`: Cancelled on POS Device `38`: Transaction Callback Failed
`Status.ErrorDescription`	String	Yes	Description of the decline reason

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Nayax Callback
This is a callback from Nayax, no response body is required. A simple 200 OK server acknowledgment is sufficient.