This paper presents a scheme for the design, analysis and comparison of electronic payment systems that extends on previously proposed schemes. The scheme has four subparts, each serving a single purpose: (i) to describe payment systems typification through common characteristics; (ii) to verify desirable requisites of payment systems; (iii) to describe system functioning from the user's perspective; (iv) to present implementation aspects of the system. Three common systems are described in detail through this scheme and many others are summarized.