are coupon codes illegal or legal? They are legal! Business use them to help get more sales. For example, a coupon code might give you a 10% discount if you buy $50 or more. Upon seeing this offer you might very well not only decide to buy from this vendor but to add stuff to your order to get to $50.Why not just reduce the price? Some people in a hurry and will buy at the regular price, no need to give them a discount.I’ve even had web sites, upon seeing that I was leaving the web site w/o buying something; offer their own coupon codes and give me a discount. A sale at a reduced price is better than no sale at all.