This thesis critically examines the fundamental determinants of the fiscal policy of the EU27 and the Republic of Croatia and attempts to answer the question: How harmonized is EU fiscal policy? The role of tax policy in situations of economic disruption is explained and the tax system in relation to capital and property tax, the effects of capital and corporate income tax are explained, profit tax in the EU27 and the Republic of Croatia is compared and an attempt is made to explain the effects of property tax. Capital taxation in the EU27 is a complex issue that affects the economic policy and competitiveness of the member states. Given the different taxation strategies of the member states, this has a significant impact on tax revenues, but also on the attractiveness of investments within the EU. Different capital tax rates in the individual countries can encourage tax planning and investment relocation. The EU is striving to harmonize tax policies in order to reduce these differences and promote economic integration. The impact of capital taxation on Member States can be both positive and negative: High tax rates can limit the attractiveness of investments, while low tax rates can reduce tax revenues and promote tax competition. The main challenges in harmonizing capital taxation in the EU include the political differences between Member States, the need to preserve fiscal sovereignty and the complexity of harmonizing tax systems.