Set up a $0 button (NON-TAXABLE) under RETAIL (not ‘food’ or ‘bev’) on the back end and name it appropriately. Follow Web > Main Menu > Custom Tenders to create this button.
On the POS ring it in and modify it with a $ amount to sell.
You can now sell the gift certificate from the POS for cash or credit and then when a customer wants to redeem their gift certificate you can ring in all their sales like normal. When ready to check out, you can press the “split” button and enter the value of the gift certificate and then select ‘other’ tenders to find the button created for this transaction.