The Constitution of the Republic of Croatia prescribes the basic principles of taxation as well as the obligation to cover public expenditures. The Croatian tax system is based on the principles of equality and fairness, and all citizens are obliged to participate in the payment of public costs in accordance with their economic capabilities. The efficiency and effectiveness of the tax system depends on the behavior of taxpayers as participants in the tax-legal relationship as well as on the behavior of the tax authority. It is the duty of taxpayers to provide the necessary information to the tax authority, to settle the obligations of taxes, contributions and other public benefits within the legal deadline, to submit legally prescribed returns and to report facts relevant to taxation. The tax authority may subsequently check the facts relevant for determining the tax liability through tax supervision, ie check the correctness of the calculation and payment of taxes and other public benefits. Verification and determination of facts relevant to taxation is based on the principles: legality, material truth, efficiency and economy. The rights and obligations arising from the relationship between taxpayers and the tax authority are prescribed by the General Tax Act, which also contains provisions on tax supervision. Tax supervision is performed by direct insight into the work and operations of taxpayers. It is carried out by authorized officials - inspectors of the Tax Administration. Based on the risk analysis and on the basis of other available data, the Tax Administration decides with which taxpayer it will conduct tax supervision. Tax supervision is a very expensive instrument of the Tax Administration and must be used rationally, and when used it must be effective. The paper defines the concept of tax supervision, who are the participants in tax supervision, principles, subject of supervision, periods, representation, exemption of inspectors, delivery of acts, deadlines and return to the previous state. The course of tax supervision is presented, as well as acts in the process of tax supervision. The paper uses expert instructions related to the tax supervision procedure, expert articles, provisions of the General Tax Act and the General Administrative Procedure Act, as well as the website of the Tax Administration.