The ease of purchasing and selling products over the Internet has helped the growth of electronic commerce and electronic payments services are a convenient and efficient way to do financial transactions. Current e-payment technologies depend on using traditional methods that are common to non-electronic systems. Due to the nature of Internet, security and authenticity of payments and participants cannot be guaranteed with technologies that are not specifically designed for electronic commerce. We need an e-payment system that would not only provide secure payments but should also have properties like online customer and merchant authentication, unforgeable proof of transaction authorisation by the customer both to the merchant and the bank, privacy of customer and transaction data. This chapter provides an overview of e-payment architecture and their functionalities, their requirements and verification of payment protocols. More thorough survey can be found in        and .