This article is aimed at evaluating and comparison various scenarios of corporate income tax, individual income tax (personal income tax) and value added tax in listed below seven post-Soviet Union republics: Russian Federation, Republic of Belarus, Republic of Ukraine, Republic of Uzbekistan, Kazakhstan, Kyrgyzstan and Moldova. For many decades, economists from the European Union and the United States have regularly discussed such problems as building optimal tax systems, greening taxation, the effectiveness of tax reforms and others. Economists of the post-Soviet space in the 90s of the last century did not have such opportunity. At the same time, there was a very high need for scientific substantiation of the tax reforms being carried out in these countries. To fill this scientific gap, two economists Igor Mayburov from Russia and Yury Ivanov from Ukraine convened the first tax symposium in the post-Soviet space in 2009. Since then, the tax symposium has been annually held in different cities and brought together leading tax specialists from different countries. Each symposium has its own thematic focus, dedicated to the most relevant aspect of taxation for the post-Soviet countries. This scientific focus is declared one and a half years before the symposium. Symposium participants conduct research and thematic monographs are prepared for each symposium. XI International Symposium "Theory and Practice of Tax Reforms", held June 30 - July 6 2019 in Tomsk on the basis of the Institute of Economics and Management of the National Research Tomsk State University. These kind of symposiums have a major aim to understand, explain and find some new solutions to make the taxation system of post-Soviet Union republics more and more developed.