You can refund a transaction when the order is either ‘paid’ or ‘shipped’. You can refund per order line, per piece, or just refund the entire order. Simply click on the refund button in the order line and confirm the refund. You can also refund the entire order by clicking the ‘Refund all’ button.
In case your customer ordered more items of the same product, you’ll also have to confirm how many products you want to refund.