I have been able to reproduce your issue. Thank you very much for pointing this out. This issue is due to the taxAmount on the payment record being null. We are aware it is not a required field on the endpoint for creating a payment record. I have opened a ticket for this issue. In the meantime, a work around would be: when you are creating the payment record, pass in a taxAmount (If there is no taxAmount on your payment, simply pass in a value of 0).