The aim of this master thesis is to describe and analyse internal control systems of two different companies from the perspective of an external auditor accomplishing a statutory audit. The thesis consists of three main parts. The first methodical part covers a description of an internal control system as a whole including its components. The second methodical part explains a role of an internal control system in the auditing process. In the third, analytical part, there are introduced two companies and their internal control systems are described. Alongside their risk analyses assessments from the auditor´s view are made, of which results influence a choice of subsequent audit procedures.Cílem této diplomové práce je popsat a analyzovat vn...