The task of tax investigation includes, among other things, the investigation of tax offenses and tax administrative offenses. Proper advice and behavior are particularly important in this area, as interventions by tax investigators penetrate deeply into the client's business and private life. Therefore, the work focuses on the responsibilities and powers of tax investigators, investigative methods, the initiation and conduct of proceedings, the advisor's response options, handling preliminary investigations, dealing with searches, and legal remedies. This work serves as a guide for the sensitive situation of the client in tax investigations, with numerous checklists and action guidelines for the advisor.