Once the gift certificate is added to the cart the customer enters an amount to redeem in the box and then continues to the confirmation page without clicking refresh. It should deduct the amount of the gift certificate on the confirmation page or go straight to the success page if one-page checkout is enabled.

There is a bug though when a customer enters and amount in the gv box and then clicks refresh. This will update the order total on the checkout page, but when they click to confirm checkout, the page will be refreshed and the gift voucher will be removed.

This will be looked into further.