Rectification of mistakes allows authorities to correct errors apparent from record within prescribed periods, with clerical exceptions and natural justice. An issuing authority may rectify errors apparent from the record in decisions, orders, notices or other documents on its own motion or when informed by an officer or affected person, subject to prescribed time limits and excepting purely clerical or arithmetical corrections; natural justice must be observed if the rectification adversely affects a person, and substantive parts of decisions or documents may not be amended in the course of such rectification.