There are 2 fields on the Product Option pages, Mail In Rebate URL and Mail In Rebate Amount. If there are mail in rebates offered with a product option, filling in these fields allows info about the rebates to be displayed on the cart and the invoice. On the cart, an extra line below the item will list the price after mail in rebate. On the invoice, a link to a rebate form will be created linking to the Mail In Rebate URL. NOTE: This functionality is not supported by the .NET cart.