Subject. Numerous scientific works in the field of tax administration are devoted to the problems of tax regulation, the imperfections of current tax legislation, as well as the identification of the causes of the functioning of the shadow economy and ways of tax evasion. However, the issues of economic security of the state and tax control in its provision have been little studied today, despite the entry into force in the legal field more than six years ago of the Decree of the President of Russia dated May 13, 2017 No. 208 "On the Strategy of Economic Security of the Russian Federation for the period up to 2030". Thus, the object of the study is tax control, the subject is the effectiveness of on–site tax control as a factor in identifying and suppressing shadow activities in order to ensure the economic security of the country and its public legal entities. Purposes. To summarize approaches to the definition of the term "shadow economy", to distinguish methods for identifying factors of business fragmentation and optimizing the tax burden. Based on the data obtained, we propose an approach to the tax administration process that allows us to quickly respond to "risk signals" in the process of selecting candidates for tax control measures and further conducting tax audits, with a high probability of their effectiveness.Relevance. Tax control is an important regulator of the economic security of the state. The issues of its improvement in order to increase its efficiency and effectiveness have been important at all times. Currently, issues related to the shadow economy are one of the urgent problems affecting the economic development of the country and the functioning of tax systems. Understanding the term "shadow economy" and developing effective counteraction methods are important for tax authorities and society as a whole.Methodology. In the existing conditions of the study, the analysis of the database of tax authorities is carried out (without providing information about taxpayers), the analysis of judicial practice, and methods of logical and statistical analysis are also used. Thus, in the course of the study, the works of foreign and domestic authors were analyzed in order to study the terms "shadow economy" and "business fragmentation". The data of statistical reporting of tax authorities are analyzed, the dynamics of efficiency and effectiveness of on-site tax control are analyzed. The arbitration practice of court cases on the application of business fragmentation schemes by taxpayers has been studied and analyzed, which made it possible to identify a number of distinctive features of business fragmentation from its optimization in order to ensure the sustainable development of organizations (taxpayers) and, based on these indicators, propose a methodology for identifying tax evasion schemes in order to select candidates for on-site tax control.Conclusions. The conducted research allows us to develop the theoretical aspects of such concepts as "shadow economy" and "business fragmentation". Having analyzed the works of domestic and foreign researchers, the author substantiates his definition of the concept of "business fragmentation". The author provides a system of the most significant indicators that can be fully taken as the basis for risk benchmarks signaling the use of fictitious tax optimization schemes by the taxpayer.