Issuing a refund
During the ordinary course of business, you might find that you need to issue refunds to customers. Amazon Payments allows you to issue refunds by using the Refund API, after you have made a Capture on a successful Authorization. Every time a successful refund takes place, Amazon sends the customer a confirmation email with details about the refund. You can issue full or partial refunds against previously successful Capture operations. A full refund includes all customer costs that are associated with the purchase. Partial refunds can be any amount between zero and the maximum defined by the service. You can issue partial refunds for selected Captures for a purchase.