The tax system encompasses all forms of taxation and is firmly integrated into fiscal policy and forms its most important part. Taxes are non-refundable, forced payments without direct counteraction, and are collected exclusively in cash. Taxes are, due to easy variability, imposing the political will of their constant research. The collection of tax revenues fulfills the fiscal goal, ie the goal of collecting such revenues is to fill the state budget and finance state needs without difficulties. The topic of this paper focuses on the explanation of the concept of corporate income tax. Corporate income tax is one of the most important forms of the tax system and belongs to the group of state taxes. It represents the tax that companies pay on the realized profit - on the difference between income and expenses. What are the problems faced by corporate taxpayers, how this type of tax is calculated, what is its financial role and how the application of such a tax has changed over time are questions that are analyzed and explained in this paper. By analyzing the state budget, conclusions are drawn on the development - increase / decrease in profit tax revenues over a certain period in the Republic of Croatia. The Republic of Croatia has undertaken a number of reforms within the Income Tax Act in order to improve the realization of certain economic effects. An in-depth study of this type of government fundraising will address all other concepts that are key to understanding one of the most important concepts of public finance.