Transactions

A transaction is a payment taken from a customer on behalf of a merchant. It is authorised, then captured, immediately by default, or later if you asked to authorise only, and may then be refunded in full or in part.

A transaction is not an order. The order is the commerce record, what was bought and what is owed; the transaction is one attempt to collect against it, and one order can have several if the first fails or the order is paid in instalments. A transaction need not have an order at all: name one when the platform is holding the line items, omit it when you only need to take a payment.

Capturing and cancelling are changes to the transaction, so they are a PATCH. Refunding creates a refund and transferring creates a transfer, so those are a POST on /refunds and /transfers.

A card payment that triggers a 3DS challenge is completed by patching the transaction with the challenge result.