Platform Docs

What is the externalPaymentId?

The externalPaymentId is an ID that the POS provides for two functions.

  1. For payments, it is an attribute that is added to the payment.
  2. For payments and manual refunds (Credit) it is also used to prevent duplicate requests from processing. If the device receives a request (Payment or Credit) with the same externalId, it will fail the transaction. This is to help in the event the POS doesn't receive a callback for some reason and/or tries to process the same transaction but the device has already received and processed the request.