20 C.F.R. § 225.56
Periodically, the Board reviews the earnings record of every retired, disabled and recently deceased employee to see if a recomputation of the PIA is necessary. When a recomputation is called for due to a change in the reported railroad or social security earnings, the Board processes it automatically. Increased benefits resulting from a recomputation are paid from the earliest month that the recomputation is effective. The annuitant does not have to request a recomputation to consider additional earnings, although the annuitant may request a recomputation before the automatic recomputation is processed. However, the effective date of the recomputation is the same, whether the recomputation is done automatically or at the request of the annuitant.
20 C.F.R. § 225.56