If you allow customers to purchase gift cards with custom amounts, you'll need to create a gift card item with no set value.
- Go to Items in the main navigation menu. 
- Press + New Item. 
- Under NAME, enter “Gift Card Custom”. 
- Under CATEGORY, select Gift Cards. 
- Under TAX CLASS, select No Tax. 
- Under PRICE, enter 0. 
- Under SKU, enter giftcard. 
- Under CUSTOM PRICE, select Enabled. 
- Scroll down and press Save. 
