The Commissioned Officers’ Effectiveness Report (COER) is the performance evaluation for Corps officers that is used as a major source of information concerning each officer’s service performance and work record. It provides a continuing documented record of an officer’s assignments, duties, and proficiencies. It is used extensively in the evaluation of officers for various personnel actions. The annual COER rating period is 1 year, which extends from 1 October to 30 September of every year. All officers on extended active duty prior to 1 July are required to complete the Annual COER.