This article shows how to use more than one of a client's Gift Card/Voucher for payment in a sale.
When you're on the Purchase screen and ready to process the payment, click the Gift Card/Voucher option as the payment method and add one of the client's gift cards/vouchers to the sale
To use another gift card/voucher in the same sale, click the Gift Card/Voucher button (this only appears after you have already added at least one gift card/voucher to the sale), then click Add new voucher. You need to generate a new voucher number > Click Create > Enter a value and click Ok. Then, select the voucher in the Payment methods pane> Enter the amount you want to use from the voucher and click Ok.