Return URLs & Callbacks

The hosted checkout flow returns the shopper to your server with a redirect. There is no separate server-to-server webhook in the sandbox.

Success and failure URLs
Set both when creating a checkout order:

callback_url — the shopper lands here after a successful payment.
failure_callback_url — the shopper lands here after a failure or cancellation.

Include your own identifier in the URL (for example ?ref=order-10001) so you can match the return to the order on your side.

Always verify
A return only tells you the shopper came back. Confirm the outcome with Get order before fulfilling the order — a cancelled payment can still hit the success URL in UAT.