Taxes harmonization is one of the elements of the ongoing integration process within the European Union. Among the arguments for the harmonization of taxes, among other things, some indicates simplification of the tax records and more effective functioning of the internal market by the neutralization of taxes in the trade and capital flow area. However, practice shows that taxes harmonization is arousing a lot of excitement, and extremely complicated process. To date attempts to harmonize taxes have encountered resistance from the Member States, as an expression of hostility to the loss of sovereignty in the tax policy sphere. In this article the author attempts to answer the question whether taxes harmonization in the European Union is possible at all. It analyzes actions taken so far in the area of harmonization and their impact on the effective functioning of the uniform internal market.