This thesis is focusing on the major trends in the tax reform in the European Union. The direction of development from direct to indirect taxes is analyzed and it attempts to find some consistent trends in taxation between selected countries within groups of new and old member states of the European Union in 1995 - 2011. Firstly the text gives the reader an introduction to tax theory and the optimal design of tax system is presented. Thesis also focuses on the issue of tax policy in the European Union. It describes the main tax policy challenges and possible design of efficiency-enhancing tax reforms. The global macroeconomic model QUEST III is being introduced. This model is widely used by international institutions for the quantitative ev...