How does Adyen respond to Payment Modification requests?

Response messages

Adyen replies to payment modification requests with a response message stating that the request has been received, for example, capture-received, cancel-received, or refund-received, and a unique PSP reference of this request. These messages mean the request is being processed asynchronously on our end.

You'll receive the final status of the modification via webhook events. These webhook events are sent as HTTP callbacks to the endpoints you set up on your server.

Tip: Read more on webhooks.