Abstract: In this article Yeremenko examines the organic relationship between the categories of equity and efficiency arising from a corresponding relationship of ethics and economics. According to the author, the relationship between ethics and economics should be thoroughly studied from the economical and philosophical points of view. The purpose of the article is to show the organic relationship between the categories of equity and efficiency arising from a corresponding relationship of ethics and economics. The author of the article tries to demonstrate the withdrawal from the ethical grounds of economics towards mathematical analysis did not lead to the desired outcome. This is proved by the fact that mainstream economics is unable to predict economic crises, on the contrary, it is the period of crisis when economics produce new movements relating economic problems to their ethical grounds. In the course of writing this research the author has used methodology of scientific theoretical analysis as well as systems approach. Based on the theoretical material, the author of the study examines the hypothesis that equitable tax system is economically effective. Examples considered by the author confirm this hypothesis, however, the problem is that the efficiency of equitable taxation is achieved in the long term, this creates certain difficulties in the process of assessing it. On the basis of the conducted research, the author developed a doctrinal definition of equity in taxation.