This chapter investigates the evolutionary process of the payment system against the background of structural changes. At the early stage, most payment systems were Designated-Time Net Settlement (DTNS) systems. Then, Real-Time Gross Settlement (RTGS) systems were introduced, which had the merit of reducing settlement risks. This first trend was followed by the deployment of Hybrid systems and Integrated systems. The Bank of Japan (BOJ) is proceeding with the Next-Generation RTGS (RTGS-XG) project. This project is regarded as a typical enhancement of payment systems following the global trend. The features and benefits of the RTGS-XG are closely analyzed.