We may revise a determination or decision after the applicable time period in § 416.1488(a) or § 416.1488(b) expires if we begin an investigation into whether to revise the determination or decision before the applicable time period expires. We may begin the investigation either based on a request by you or by an action on our part. The investigation is a process of gathering facts after a determination or decision has been reopened to determine if a revision of the determination or decision is applicable.

(a) If we have diligently pursued the investigation to its conclusion, we may revise the determination or decision. The revision may be favorable or unfavorable to you. “Diligently pursued” means that in light of the facts and circumstances of a particular case, the necessary action was undertaken and carried out as promptly as the circumstances permitted. Diligent pursuit will be presumed to have been met if we conclude the investigation and if necessary, revise the determination or decision within 6 months from the date we began the investigation.

(b) If we have not diligently pursued the investigation to its conclusion, we will revise the determination or decision if a revision is applicable and if it will be favorable to you. We will not revise the determination or decision if it will be unfavorable to you.