One of the main reasons for the implementation of tax audits is the existence of the informal economy. Today, more or less informal economy is seen in underdeveloped, developing and developed countries. Therefore, preventing the informal economy is one of the main goals of all countries. Informal economy is a problem that we encounter in many areas, one of which is taxation. The taxation of the informal economy is that legal or illegal activities cannot be detected or that activities cannot be taxed at the required level after detection. At this stage, tax audits become important. In particular, adequate taxation of the activities that cause the taxable event and deterrence of the penalties applied as a result of tax audits are important in ensuring an effective tax audit system. In case the tax audits do not work effectively, some taxpayers turn to informal activities by using various methods. This situation damages the sense of justice of honest taxpayers who pay their taxes fully and completely, and encourages unregistered economic activities by reducing their voluntary compliance with tax. In this study, the role of tax audit in ensuring transparency and preventing informality is evaluated. In order to prevent the informal economy, first of all, an effective tax control system should be provided. In this way, both the informal economy can be prevented and transparency can be ensured.