1 Lomonosov Moscow State University, Moscow, Russia The presented research reveals an approach to the construction of a legal mechanism for the functioning of payment systems. The proposed approach is based on the application of the principles of legal regulation. The purpose of a work is to determine the existing legal mechanism for the functioning of payment systems, identify its drawbacks and propose a new approach to legal regulation to ensure the proper functioning of payment systems. The proposed approach to legal regulation takes into account the specifics of the functioning of payment systems, which consists in the presence of three elements in its activities: institutional, procedural and organizational. These elements reflect the subject structure of the payment system, the process of providing money transfer services by them, and the ways in which payment system entities interact during providing payment services. Each of the elements must be defined within the legal framework of the payment system to ensure its proper functioning. The proposed principles of legal regulation take into account the features of these elements, in particular, the principles are classified into three groups, depending on the element they affect. The paper describes ways to implement the principles in the legal mechanism: the possibility of their direct application, depending on the type of significance of the payment system, is analyzed. It is also concluded that the implementation of the principles in the legal mechanism will reduce the regulatory burden on payment systems by using an approach depending on the level of significance of the payment system. The paper defines the role of the principles, which is that the principles allow to eliminate the legal gaps in the legislation on the national payment system, and prevent the emergence of new gaps.