Errors

Errors use the GOV.UK Pay shape. field is only present for validation errors.

{ "field": "amount", "code": "P0101", "description": "Missing mandatory attribute: amount" }

HTTP status	Code	Meaning
400	P0197 / P0697 / P2197	The JSON in the request body is invalid.
400	P0601 / P0602	Refund amount missing or invalid.
400	P1211	No payment matches the one_time_token.
400	P2501	The agreement is already cancelled or inactive.
401	n/a	No bearer token sent. Body is {"message":"Unauthorized"}.
402	P0010	The card was declined (POST /v1/auth).
403	n/a	Bearer token sent but not valid. Body is {"message":"Forbidden"}.
404	P0200 / P0300 / P0500 / P0600 / P1000	No payment matched the ID.
404	P0700	No refund matched the ID.
404	P2200 / P2500	No agreement matched the ID.
404	P0402 / P1100 / P1402 / P2402	The requested page of search results does not exist.
409	P0191	The Idempotency-Key has already been used.
409	P0502	The payment cannot be cancelled in its current state.
409	P1003	The payment is not capturable.
412	P0603 / P0604	The payment cannot be refunded, or refund_amount_available does not match.
422	P0101 / P2101	A mandatory attribute is missing. See field.
422	P0102 / P2102	An attribute value is invalid. See field and description.
422	P0104	return_url cannot be used with moto_api.
422	P0401 / P1101 / P1401 / P2401	A search parameter is invalid.
422	P1212	The one_time_token has already been used.

Codes P1401 and P1402 (disputes search) are assumed; the public documentation does not list them.