To issue a refund for an order, you have two options:
1 - Refund from the PrestaShop Back Office
From your PrestaShop interface, go to the order in question via Menu > Orders > Orders.
To issue a total refund for the order, you should change the order status to “Refunded”. The full order amount will be refunded and you will find the refund in the list of your transactions for the order and in your activity overview on www.paypal.com
To issue a partial refund, click on “Partial refund” at the top of the order. You’ll be redirected to the bottom of the order page, where you can enter the number of products concerned by this refund and the amount to be refunded for the products and for the delivery. You also have the “Re-stock products” option if a product has been returned in good condition. Click on “Partial refund” at the bottom to confirm. The equivalent amount will be refunded and the status of the order will be “Partially refunded.” You will find this refund in the list of your transactions for the order and in your activity overview on www.paypal.com
2 - Refund via the PayPal interface
Once you log in to www.paypal.com and go to the Activity tab of your PayPal account, all completed payment transactions can be refunded through the “Refund” button to the right. When you click on it, you are redirected to a refund page that summarizes the amount of the order and allows you to enter the total amount of the refund.