Learn about documenting your department's key control activities to mitigate financial errors. As outlined in the required key controls that your department must perform and cerify these controls: A key control is an action your department takes to detect errors or fraud in its financial statements. Your department should already have key financial review and follow-up activities in place. To fulfill documentation requirements, departments should review those activities and identify key controls. The first steps are to determine: 1  Key controls exist.