Abstract: The subject of the research is the mechanism of interaction between tax authorities and internal affairs bodies aimed at discovering illegal schemes of tax avoidance in the process of tax control. The purpose of this article is to define drawbacks and gaps in the aforesaid process as possible factors that may reduce efficiency of their joint efforts. The author pays special attention to the place and role of internal affairs bodies in the process of tax control and tax relations in general. In the course of her research the author has used the following research methods: economic statistical, historical logical, graphical methods and systems approach that allows to comprehensively study the process of interaction between tax authorities and internal affairs bodies. The author's contribution to the topic is that she defines and describes a number of problems that may arise in the process of their interaction and offers solutions of these problems. As a conclusion of the research, the author emphasizes the need to clarify the status of internal affairs authorities in tax control as well as the need to involve internal affairs bodies in tax relations.