Management Accounting and Internal Auditing are traditionally two autonomous, from each other independent management tools, which are used for the purpose of controlling and monitoring. The main distinguishing feature is the time component. Internal Auditing mainly carries out ex-post considerations, whereas the tasks of Management Accounting can be seen in an ex-ante consideration. Due to the increase of ex-ante audits in operational and management auditing as well as consultancy services by the internal audit function, overlaps can occur between both fields. The tasks of Management Accounting and Internal Auditing are extended continuously through an increased Corporate Governance. The applications of Internal Auditing under Sarbanes-Oxley Act are investigated and, in particular, the disclosure controls and procedures under Section 302 und 404. Concerning the association between corporate governance quality and disclosure of material weaknesses in internal control over financial reporting, there is a difference between the requirements Section 302 und Section 404. The internal control system is part of the risk management system, wherefore the targets of Management Accounting and Internal Auditing are investigated in those areas. In recent years several serious corporate collapses are, among other things, due to accounting fraud. Investigations show, that a high quality of the internal audit function can curb the extent of accounting fraud. Whistle-Blowing can contribute to the identification of management fraud. Management Accounting and Internal Auditing are playing a central part also in this area.