The comparable amount of the overall taxation of the incomes of self-employed, employees and single directors is significantly influenced not only by tax rates, but also by the assessment bases for income tax and social security contributions. Unlike western countries, we have a low tax rate on the income of natural persons and a high burden on work through social security contributions, the lion share of which is paid by the employers. The prerequisite for the effective solution of the problem of the overall taxation of self-employed includes clarification of the concept for financing social security, from which the expediency of combining the current taxation of personal incomes with the social security contributions paid by employees becomes apparent under Czech conditions. At the same time, this will also involve a necessary increase in the tax rates for self-employed and single directors. The rate of the social security contributions paid by employers and self-employed may be differentiated on the grounds of the lower scope of social security provision for self-employed, but this is not necessary under Czech conditions. The allowance for employee benefits (in particular paid leave) provides justification for the reduction of the assessment base for self-employed social security contributions to below the level corresponding to the share of an employee gross wage in the total labour costs.