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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.

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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"
  }
}

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Request Parameters

The table below describes the parameters of the request:
FieldTypeRequiredDescription
MachineIdIntegerYesThe ID of the vending machine or terminal
HwSerialStringYesSerial number of the hardware terminal
SparkTransactionIdStringYesThe unique identifier of the failed Spark transaction
StatusObjectYesAn object indicating decline details
Status.VerdictStringYesAlways “Declined”
Status.ErrorCodeIntegerYesDecline reason code
  • 44: Timeout on POS Device
  • 45: Cancelled on POS Device
  • 38: Transaction Callback Failed
Status.ErrorDescriptionStringYesDescription of the decline reason
Nayax CallbackThis is a callback from Nayax, no response body is required. A simple 200 OK server acknowledgment is sufficient.