How do I set a tax % for specific items in the cart? Add items to your cart Edit Item Enable/disable Tax for this specific item using the toggle button (if you don’t see a Tax row, it’s because Tax is disabled in the app settings). You can also use this dialogue box to edit the tax percentage for this specific transaction. Tap the check-mark in upper right-hand corner to save. For additional support, please refer to the Support Page in your merchant portal or contact your ISO contact.