The object of the study is the social relations that developed after the introduction of the tax on professional income. Not only the legal relations regulated by Federal Law No. 422-FZ dated November 27, 2018 "On conducting an experiment to establish a special tax regime "Tax on professional income" are being studied, but also the employment relations of persons who have switched to this special tax regime. The author examines in detail such aspects of the topic as: the dynamics of the number of self-employed, the structure of self-employment, the ratio of self-employment and traditional forms of employment, the socio-economic consequences of the experiment, the importance of the tax on professional income for the economic security of Russian society. Thus, the subject of the study is the socially significant consequences of conducting a tax experiment, the influence of specific legal norms on the whole set of public relations is studied. The methodological basis of the research is dialectical materialism. The object of research is considered comprehensively and in connection with other phenomena of social matter. General scientific and special research methods are used to collect, process, generalize, analyze and interpret the material: induction, deduction, document analysis. The novelty of the research is determined by a number of aspects. Firstly, the social relations caused by the introduction of a tax on professional income are analyzed comprehensively in all their diversity, not limited, as is often the case, to the fiscal component. Secondly, current empirical data are being investigated not only by tax authorities, but also by other government agencies and public organizations. Thirdly, for the first time, the socio-economic essence of the tax on professional income is exposed, and its significant disadvantages are shown on specific empirical data. Taken together, these circumstances allow us to formulate a conclusion about the impact of the tax regime in question on a key element of the country's economic security. The author formulated a hypothesis about the possibility of overcoming existing problems and justified the need to change existing approaches to regulating public relations in the field of self-employment.