The study of the institutional foundations of budget planning determines the activities of institutions in the field of forming the revenue part of the budget, effective planning of the expenditure part, ensuring the balance of the budget and increasing the level of macroeconomic balance, which is especially relevant during the period of martial law in order to adapt the institutional environment to social, economic and social transformations in the country. The institutional environment of budget planning is important, as one of the main regulators of budget relations, with the aim of ensuring macroeconomic balance both in the short-term period and in the medium-term perspective. Adaptation of the institutional environment to social and economic changes and determination of priority directions for the further development of financial and budgetary relations require attention. The article aims to reveal the institutional foundations of budget planning in the system of macroeconomic regulation. The main research methods are dialectical and systemic. Structural, comparative, factorial and logical methods were also used. In the course of the research, the essence of the institutional environment of budget planning was determined, the content of the budget institute and the budget policy institute was revealed. Adaptive changes in the institutional environment of budget formation, which were caused by the start of a full-scale war, are analyzed and priority directions for further improvement and development of the institutional environment of budget planning are given. Effective institutional environment of budget planning has a significant impact on the level of macroeconomic balance, social and economic development of the country and achievement of priorities determined by medium-term social goals. The state of war on the territory of Ukraine has become a rather significant challenge, including for the financial and budgetary institutional environment. The conducted study of the current legislative framework indicates a gradual change in the institutional environment of budget formation before transformations in social, economic, and public relations. Further improvement and development of the institutional environment for budget formation in terms of creation and implementation of effective financial mechanisms is appropriate, in order to ensure macroeconomic stability and further socio-economic development of the country.