Abstract: The article analyzes the peculiarities of realization of the principle of division of powers in the budget system of the state; the structure of authorities involved in budgeting. The article is also devoted to a special feature of the legal status of the state, municipal units and their authorities – budget competence (budget rights and duties). The author considers budget competence as a special element of the budget system of modern Russia. The issues, considered in the article, are among the urgent problems of financial and legal science. The methodology of the research comprises general scientific methods (analysis, synthesis, abstraction and concretization) and special scientific methods (formal-logical, comparative-legal, system-structural, historical-legal, logical methods and legal modeling). The novelty of the research lies in the formulation of an approach to the structure of elements of budget system, taking into consideration that the concept of budget system is not explained in the existing legislation; in the analysis of a nature of budget system from the positions of the principle of division of powers with the emphasis on realization of executive and legislative authorities in the sphere of budget relations.