<p>Tax evasion causes a significant loss of revenue from the state budget not only in the Slovak Republic but also in the European Union. Therefore, European Union countries are looking for ways to detect tax evasion. It is not possible to eliminate tax evasion, but it is possible to effectively detect and combat tax evasion through legislation as well as through effective tax control. This paper aims to outline the theoretical as well as practical approach to quantifying tax evasion and to make recommendations aimed at reducing the tax gap</p>