Coupons are invented by companies in order to prosper. It is interesting to explore how they, being just a piece of papers, can do that. Coupons help companies to increase sales on those people who evaluate their effort to obtain coupons lower than the benefit from coupons. When we see the ordinary discounts, we might consider coupons as being odd and complicated, but their usefulness can be proven with theoretical and practical evidences. We know what do they look like, where to find them, who are using them, but do we know in which circumstances they are or are not helpful for firms? It requires a much deeper insight into this issue. People use them overwhelmingly, although many of them do not have any idea how can coupons make firms better off and how do they work. Therefore, it would be appropriate to answer these questions, explain the rationality and efficiency of coupons. …