The article deals with issues of taxation of sportsmen in the Czech Republic. Categories of sportsmen are defined in the theoretical introduction, divided into amateurs, semi-professionals and professionals. These categories are then linked to specific sections of Act on Income Taxes, which are applicable to the taxation of sports activity. The theoretical part is followed with quantification of income tax, social security and health insurance, using a model example with various levels of taxable incomes. All the calculations apply both to the situation where the sportsman assumes the position of an employee, i.e. he has an employment contract, and where he is a self-employed person. Tax incidence on various groups of people involved as well as effects on the public budget are measured within the defined categories. In the context of the public budget we work with the concept of tax evasion which arises from the utilization of one or the other form of relationship between the sports club and the sportsman.The model example is followed with concrete measurements of tax evasion in football in the Czech Republic. We work with specific publicly available data concerning taxable incomes of professional football players in the top Czech football competition - Gambrinus liga. In conclusion, the interdependence of defined quantities is measured using Pearson product-moment correlation coefficient.