Tax supervision in the Republic of Croatia is regulated by a number of laws and bylaws, of which a special place is occupied by the General Tax Law. Tax supervision is a tax-legal relationship in which the Tax Administration and the Customs Administration and other tax authorities carry out a procedure to verify and establish facts relevant to the taxation of taxpayers and other persons. Tax supervision can be performed by the auditor, tax inspector and other civil servants authorized for its implementation, and when performing tax supervision they must act in accordance with the principles of tax supervision: the principle of legality, the principle of material truth and the principle of efficiency and economy. The aim of the final paper is to determine and explain what tax evasion is and the course of tax supervision if it becomes known that the taxpayer has committed some form of evasion.