After the customer make any transaction (e.g success, fail, cancelled), edxaPay will notify the callback URL to notify the merchant about the payment status.
There are 2 ways to set the return URL.
- Fixed URL via dashboard
- Via API call parameter. Refer this link
Fixed URL via Dashboard
Follow the steps in the image below

What Happens If No callback URL ?
If no callback URL provided via the dashboard or the API, the merchant have no way to verify if the payment was successful or not. If you are integrating to a system, your sales order or invoice will not be updated with the payment status.