To refund a payment to your customer, all you need to do is follow the below steps on a payment after it has reached the status of CAPTURED or SETTLED/SETTLED_BY_MERCHANT.
In the Merchant Admin Interface click Transactions on the left-hand menu and then Payments.
Choose the Amount link of the required payment to display its details, and navigate to the Refund section.
To refund less than the full amount, change the refund amount (you can't refund more than the full amount).
Click the Refund button, and confirm by clicking Yes. If a refund completion form pops up, this is because we need more information to process the refund
The refund request is now sent, and the refund process starts.
Note: For some payment methods, the refund button is not visible because the refund cannot be completed online. In this case, please contact our Customer Support.