Building an optimal tax system is a strategic objective for any state. Under the conditions of the economy openness, both internal and external factors can have a significant impact on the pace of economic development of a country that affects the level of tax collection. The article both emphasizes the importance of tax system improvement and explains the necessity of tax administration optimization. A tax system approximated to optimal one will be less affected by the negative trends and modern tax administration will reduce costs, increase transparency and the taxpayers’ trust level. The tax system analysis was carried out based on studying the Visegrad Group countries’ experience (the Czech Republic and Poland), as well as Georgia and Belarus. As a result, it was observed a single direction of all countries’ development in the area of the tax system improvement, while the presence of the individual characteristics.