Contemporary crisis phenomena, including financial, structural, political, and social aspects, underscore the need for effective fiscal policy to ensure the resilience and development of the country. Additionally, there are currently complex challenges related to the war, such as infrastructure destruction, business shutdowns, and mass migration, which have significantly impacted the country’s economy and require additional financial resources for recovery. This situation necessitates the search for new sources of income and the optimisation of existing resources, highlighting the importance of effective tax regulation to overcome economic challenges during conflict. This scientific article aims to determine the role of fiscal policy in ensuring effective economic development, as well as the importance of tax instruments and their efficiency in promoting economic growth and optimising financial resources. In the research process, literary sources were analysed, and statistical data was scrutinised to evaluate the dynamics of state revenues and expenditures and the impact of tax receipts on the state budget. The study emphasises the importance of tax instruments for economic development and meeting the country’s financial needs. The efficient use of tax instruments facilitates the collection of sufficient revenues to fund social and economic needs. The study highlights the importance of employing the necessary tax instruments to ensure the country’s effective economic development. In martial law conditions, mobilising fiscal reserves and activating tax instruments become critical strategies for ensuring financial stability and supporting the economy. However, the successful implementation of these measures requires the improvement of the organisational structure and administration. A balanced approach to tax burden, a conducive environment for business, and the development of new revenue sources are critical in ensuring financial stability and supporting economic growth during conflict.