The article considers the current challenges of ensuring the economic and tax security of Ukraine in the conditions of martial law, which has been in effect since February 24, 2022. The author emphasizes that the economic security of the state is inextricably linked to tax security, because taxes and fees, in particular from small and medium-sized businesses, are key sources of financing the security needs of the state. It is noted that the current regulatory and legal framework in the field of economic security is mainly declarative in nature and does not contain clear mechanisms for implementing tax security. Particular attention is paid to the simplified taxation system, which in modern conditions, in the author's opinion, poses a threat to tax security, as it contributes to incomplete tax revenue to the budget. The work justifies the need to revise the principles of functioning of this system, and its complete removal from tax legislation. The author emphasizes the importance of a comprehensive approach to improving tax policy both in wartime and during the period of post-war reconstruction of the country. The focus of the study is on finding ways to achieve a balance between supporting entrepreneurship and ensuring stable revenues to budgets of all levels as the basis of national security in a broad sense.