The internal control system of financial institutions in Korea is mandatory since relevant financial institutions are required to have internal control system as mandatory legal obligation. Under such mandatory internal control system, the system cannot function as intended without being efficient. However, since such mandatory internal control system had implemented, repeated major financial incidents of banking and non-banking institutions made the Financial Supervisory Service in Korea require improvement of internal controls to the financial institutions, and even the Bill of the Act on Governance of the Financial Companies has provisions to improve internal control of the financial companies. The discussions on the change and improvement of internal control system in financial institutions came from the understanding that the internal control system would not function as intended. Since negative control such as supervision and sanction need constant control by the supervisory authorities, positive incentives need to be used to encourage motivation of the financial institutions. For such purpose, it can be considered that the central bank has the power and authority to evaluate the efficiency of the financial institutions and rate the efficiency. The Bank of Korea as institution to implement the stability of financial system could exercise its inspection or joint inspection power to evaluate the efficiency of internal control system in financial institutions. If a financial institution gains higher rating on the efficiency of its internal control, positive benefits such as regulations on interest rate of deposit or loan, the limit of total amount of lending, and the regulation on collateral lending. Moreover, since the central bank decides its monetary policy which has significant influence on financial market, the Bank of Korea needs its own internal control system to obtain the trust from the market regarding the policy and its implementation.