ACI Open Payment Platform — Server-to-Server API
The core RESTful payment API of the ACI Open Payment Platform (PAY.ON gateway). Server-to-Server integration lets merchants and PSPs run end-to-end payment workflows — preauthorization, debit, capture, refund, and reversal — across cards and alternative payment methods. Requests are authenticated with an Authorization Bearer access token plus a channel entityId. Production host is https://eu-prod.oppwa.com and test host is https://eu-test.oppwa.com.