(40)It is of importance that competent authorities as well as delegated bodies and natural persons to which certain tasks have been delegated, ensure and verify the effectiveness and the consistency of the official controls they perform. For that purpose they should act on the basis of written documented procedures and should provide information and instructions to staff performing official controls. They should also have appropriate documented procedures and mechanisms in place to verify continuously that their own action is effective and consistent, and take corrective action when shortcomings are identified.