A study of the level of tax harmonization in the countries of the Eurasian Economic Union has been carried out. The points of view of various authors on the problems of tax harmonization and tax competition are considered. The objectives of the study are to assess the degree of tax harmonization of the EAEU countries, as well as to analyze the impact of tax harmonization on economic growth. The study used econometric methods of macroeconomic analysis. It has been established that despite the rather long time that has elapsed since the creation of a single economic union, tax harmonization has not taken place in the EAEU countries. The size of the main tax rates in the EAEU countries differs significantly. The highest level of tax burden is in Armenia. The least time is needed to prepare and pay taxes in Russia. The smallest share of income tax in the total profit of companies is paid by Kyrgyz taxpayers. In turn, the lack of tax harmonization in the EAEU creates preconditions for tax competition between countries, associated with the creation of attractive conditions for taxpayers who will be ready to transfer their business to the country with a more favorable tax regime. As a result of the study, it was found that in conditions of tax competition, Russia and Kazakhstan are in the most advantageous position. The study revealed the negative impact on economic growth of a high tax burden and a significant length of time required for the calculation and payment of taxes. A close correlation has been established between total tax revenues and the growth of the economies of the EAEU countries.