Currently if you are fulfilling/returning a sales order, you are unable to add a gift card and refund the amount of the sales order. For cash and carry transactions you can add a gift card to the return transactions and can book the refund on the Gift card. The same cannot be done for sales order during the return. You either need to issue a gift card which you can only with min 0,01 cent which again creates a difference in the till. Then you can use the gift card payment method to refund this. There should be a possibility to do a refund by issuing a new gift card also during the return sales order process.