Pay fast Charges 3.5% for transactions. We run at a 2.5% margin and lower. If a customer decides to use Pay Fast we need the site to add 3.5% to the price and show this charge to the client as Pay Fast. We need the same done for Cash deposits, but at 1.5% added and displayed. On the check out page we also need an (Accept Terms & Conditions) check box to Finalize Checkout.