16. Revision
(1) The Commissioner may, call for and examine the record of the proceeding of any order made by the assessing authority, or the appellate authority for the purpose of satisfying himself as to the legality or propriety of such order and pass such order not prejudicial to the interests of revenue.
(2) [x x x]
(3) The powers of revision shall be exercised within such period not exceeding four years from the date on which the order was served on the assessee.
(4) No order which adversely affects any assessee shall be passed under this section, unless such assessee has been given a reasonable opportunity of being heard.
(5) [x x x]
Rule 22 , Form XII