The cash system is one of the most important characteristics of Financial Law. The state of public finances, the effectiveness of the budget process in general, and the execution of the budget in particular depend on the choice of the cash system. The centralization of public power and the need to improve state financial control led to the transition from a decentralized cash system to a unified cash system. In Russia, the establishment of the principle of unified cash in budgetary law was associated with the Tatarinov reforms of the 1860°. The Russian historical experience provides a normative and empirical material for understanding the principle of unity of budget account. Throughout the 19th and 20th centuries, all known models of the cash system were used in Russia: the treasury model, the banking model, and the mixed model. The development of Russian budget legislation in the 21st century creates new contours of organizational and legal forms for the cash execution of the budget. Changes in the political and economic situation in the country, as well as improvements in information and communication technologies, are leading to the emergence of new institutions in the field of Budgetary Law. The creation of the treasury payment system in the early 2020s led to the unification of treasury and banking functions within the Russian Treasury, thereby overcoming the antagonism between the banking and treasury models of the state's cash system.