Add this mod to your store and you'll be able to offer your customers a discount Coupons or Vouchers.

You can create an unlimited number of discount coupons. Each coupon can be custom configured to apply discount by dollar amount or percent off, i.e. $5 or 10% off the price of an item or the entire order.
You can also restrict coupons to be applied only to a specific item or to the entire order. Additional use restrictions include number of times a coupon can be used and coupon expiration dates.