In the article, the author studies the problem of implementing the principle of equality in the taxation of windfall profit. For this purpose, the content of the principle of equal taxation is analyzed on the basis of the Tax Code of the Russian Federation provisions, Russian Constitutional Court’s practice and tax law doctrine. The author correlates the content of the principle with Russian windfall tax regulatory peculiarities. In this regard an analysis of several provisions of the federal law on the specified tax is carried out with respect to their interpretation, given by Russian Constitutional Court in Decision № 3214-O of December 4, 2025. Based on the results of the study, the author comes to the conclusion that ensuring of the implementation of the equality principle in the taxation of windfall profit implies fixing the following general rule: all business entities should be recognized as payers of the relevant tax. Exceptions should be due to objective economic and/or legal factors, such as non-achievement of a payback rate, use of other fiscal mechanisms for the withdrawal of excess profit, existence of specific sectoral legal regulation and exclusion of contradictions allowing for different application of rules on windfall profit tax.