The essay is devoted to the legal nature of legal tender. The author considers it as a monetary legal regime. The work presents the history of legal tender, developed a theoretical concept of this legal phenomenon (concept, features, features, types), resolved current problems that arise in practice (legal tender in unrecognized and partially recognized states, the relationship between legal tender and the contract of exchange, the introduction in Russia of a new form of national currency - the digital ruble). The essay will be of interest to students and practicing lawyers, academics and researchers in the field of monetary regulation.