The internal control system is examined as a variety of internal control of an economic entity on the one hand, and as the foundation for transitioning towards tax monitoring on the other. Such approach allows assessing this structure from the perspective of taxpayers, as well as from the standpoint of implementation of public function of tax control. The object of this article is the process of improving internal control system of tax obligations by the taxpayer in the conditions of digitalization of tax administration. The subject of this article is the theoretical aspects of internal control as an administrative function, as well as comparative analysis of the Russian “internal control” system with the classical COSO model. The scientific novelty consists in comprehensive research of the internal control of tax obligations, determination of its essential characteristics,  and assessment of the consequences of formalization of requirements thereof, which led to the conclusion on transformation of the internal control of the taxpayer from the area of reputational merits of the economic entity and internal administration instruments to the subject of public control by tax authorities in tax monitoring processes. It remains to be seen whether state interference in such delicate sphere of activity of an economic entity as internal control is justified. The goal of this research consists in the analysis of the effective requirements of the Federal Tax Service of Russia from the perspective of possibility of their implementation by the particular taxpayers. The article provides the examples of assessment of certain components of the internal control system based on the criteria set by the Federal Tax Service of Russia. The author formulates the definition of control procedure, carries out classification of the aforementioned criteria; develops the examples of effective design of some controls; as well as presents the examples of assessment of IT systems from in the context of extended requirements of the Federal Tax Service of Russia.