Rectification of errors apparent on the face of record permits correction of obvious mistakes within prescribed time, preserving natural justice. Any authority that has issued a decision, order, notice, certificate or other document under the Act may rectify errors apparent on the face of record on its own motion or when notified by an officer under this Act, an officer under the Central Act, or the affected person, within the prescribed short period from the date of issue, subject to an overall outer time limit and an exception permitting correction of clerical or arithmetical slips arising from accidental omission; where rectification adversely affects any person, principles of natural justice must be followed.