AR 623-3 page 34 states: 3-2 g. Retirement OER or NCOER requirements include the following:
(1) All Soldiers will receive an OER or NCOER within 12 months before the first day of transition leave. Retirement OERs or NCOERs of less than 1 calendar year are optional. These reports will be rendered at the option of the rater, senior rater, or when requested by the rated Soldier (see para 3–44c). Retirement reports that conclude a Soldier’s military career, if rendered, will have a “Thru” date that is the final day of supervision or last duty day before beginning transition leave (or before the effective date of retirement, if no transition leave is taken).