Attach a proof of payment to a payment: a bank confirmation or EFT slip supporting an outcome recorded by hand with record a payment outcome.
Attaching a file changes nothing about the payment itself, and there is no status restriction: a proof can be attached before, after, or long after the outcome is recorded. Files accumulate rather than replace, so list them with list proofs of payment.
Recording payment outcomes is opt-in per organization: unless the manual_payment_outcome feature flag is enabled for your organization this endpoint returns 403.
Validation error. Examples: file_type is not one of the three accepted types, the file's contents do not match the declared type, or file_name's extension does not match its contents.
Recording a payment outcome is not enabled for the organization, or the caller is missing the payments:external:update permission.
No such payment.