This paper analyzes the legal and theoretical structure of the corporate income tax in various forms of its existence and implementation in practice through the prism of the vertical and horizontal components of the principle of fairness as one of the fundamental normative principles of the tax system. The abstract nature of such a principle, which includes ethical and moral components of its legal definition, is especially taken into account, in relation to the existence of the corporate income tax, which is also problematic in itself, given that according to its legal regulations, it refers to legal entities, while its final incidence necessarily affects natural persons. The basic thesis of the paper, therefore, starts from the fact that the corporate income tax is undoubtedly an existing component of all modern fiscal systems and that its doctrinal questioning remains exclusively in the sphere of legal theory. There are, however, problems with its implementation in practice, especially in cases where double taxation is generated in the context of national, as well as international and global trade, with the danger of weakening economic entities directly affected by such a tax burden. The principle of fairness is useful for preventing the harmful effects of this tax and for avoiding possible obstructions in the development of business and the expansion of companies. This paper also criticizes the very present populist views that legal entities of this type should bear the extremely high rates of tax liability due to the fair social distribution of capital. Such efforts, in addition to being difficult to achieve precisely because of the existing difference between the legal and economic incidence, weakens the economic strength of the corporate sector, which as a result has repercussions on the market as a whole, negatively affecting all natural persons directly and indirectly involved in the economic activities of the most diverse companies profiles. The outcome of such efforts is precisely the violation of the vertical and horizontal dimensions of the principle of fairness.