The aim of this paper is to present the institutional features of the European Commission as one of the most important institutions of the European Union , to determine the European Unionʼs financial interest and the notion of protection of financial interests , and to show the activities undertaken by the European Commission to prevent or reduce the number of tax frauds and tax evasions, in order to protect the EU budget. It briefly describes the establishment and competence of the European Anti- Fraud Office , the meaning of the Directives on combating fraud against the financial interests of the European Union through criminal law ( PIF Directive) which was adopted on a proposal from the European Commission , it describes the objectives of the European Anti – Fraud Strategy adopted by the European Commission, outlines the goals and purpose of the European Commission program Pericles and Hercules, and analyses need and purpose if establishing the Office of the European Public Prosecutor, wich was established on the proposal of the European Commission but has not yet started to function. The paper concludes with brief overview of how to Croatian Tax Administration fights tax fraud after Croatiaʼs accession to the European Union and what activities it undertakes to detect them in a timely manner, adequately sanctioning and taking preventive action to reduce their numbers , in order to protect the budget of the Republic of Croatia and those taxpayers who fulfil their tax obligations in full and within the statutory deadlines.