The Internal Audit provides independent and objective auditing and consulting services on behalf of the company's management. This distinguishes it from other internal control functions, such as controlling. The Internal Audit creates added value by improving business processes. A similar approach is taken by compliance, which is increasingly prevalent in German companies. It is also operationally active. The work describes in its second edition the fundamentals for an effective Internal Audit. At the same time, it examines the relationship with compliance from both operational and legal perspectives. Specifically, the connection between operational aspects and relevant legal issues, such as the KonTraG, BilMoG, DCGK, and liability law, is the unique selling point of this book. Key focuses include the requirements for a modern Internal Audit as well as the most important audit areas.