(1) The appellate authority may at any time withm three years from the dale of an order passed by him on appeal and the assessing authority may at any time withm three years from the date of any assessment or refund order pasc;ed by him, of his own motion, rectify any mistake apparent from lhe record of the appeal, assessment or refund, as the case may be, and shall Within the hke period rectify any such mistake which has been broug},t to his notice by an as1>essee : · . _,.
Provided that no such rectification "hall be made having the effect of enhancing an assessment or reducing a refund unless the assesc:ee has been given a reasonable opportunity of bemg heard m the matter. ' '
(2) Where any such rectification has the effect of reducing the assessment, the assessing authority shall make any refund which may be due to such assessee.
(3) Where any such recllfiC'ation.has the effect of enhancing the assessment or reducmg a refund, the assessmg authority shall serve on the assessee a notice of demand m the prescr1 bed form specifymg the sum payable; and such notice of demand shall be deemed to be Issued under section 8 and the provisions of this Act shall apply accordingly. 1