At the moment, the unbalanced state of the fiscal system is provoked by overstated expenditure commitments of territorial entities and a large-scale centralization of tax authorities. To overcome this imbalance by paying off the deficit of regional budgets, shifting spending responsibility from one level of the budget system to another, or making minor tax adjustments are not enough. A systematic approach is needed to reform budgetary interactions between the federal center and the subjects of the federation. The article deals with theoretical foundations and content parameters of building an institutional fiscal system. The authors define the institutes-determinants forming the institutional conditions of budgetary-tax regulation. We carried out the analysis of institutes-determinants and their interaction on the basis of the complementarity principle. The authors have revealed that an important component of a balanced fiscal system is the correspondence of its formal characteristics of the institutes-determinants to informal rules. The lack of institutional complementarily generates various negative informal consequences.