The article comprehensively analyzes the theoretical foundations and practical aspects of financial controlling of transactions with securities in view of the peculiarities of their taxation. Possibilities of improving controlling to increase the efficiency of securities management at enterprises are considered. The essence and functions of financial controlling in the financial management system of modern enterprises are analyzed in detail. thus, such key functions as strategic planning of financial activities, budgeting and financial planning, internal consulting and auditing, constant control and analysis of financial indicators for the presence and nature of deviations are defined. The article presents the classification of securities and describes the stages of financial control of operations with them. such as strategic planning of the optimal investment portfolio, budgeting of investment volumes in various instruments, adjustment of the accounting and reporting system for operations, as well as optimization of their taxation. A detailed procedure for the analysis of tax transactions with securities in Ukraine has been carried out. which determined the rates of income tax and military levy, the procedure for calculating investment income. Particular attention is paid to the possibilities of tax optimization by using the benefits provided by the law for long-term investments or carrying out operations through offshore jurisdictions with a favorable regime. It is important that the enterprise fully complies with both the legislation of Ukraine, which includes operations, and the legislation of those countries in which placement, purchase or sale of securities takes place. A detailed analysis of tax regulation in Ukraine, including tax rates and opportunities for tax optimization, makes the article a crucial source of information for enterprises engaged in operations with securities. It is noted that financial controlling is a key tool in managing such operations, and the examination of taxation specifics unveils opportunities for tax burden optimization and overall enhancement of financial management efficiency for businesses. It is shown that financial controlling is the main tool for managing transactions with securities, and the analysis of the peculiarities of their taxation provides opportunities for optimizing the tax burden and increasing the overall efficiency of the financial management system of enterprises.