Rectification of mistakes

(1) The authority which made an assessment or passed an order on appeal or revision in respect thereof may of his own motion, and shall if an application is filed in this behalf, within three years, from the date of such assessment or order rectify any mistake apparent from the record of the case: Provided that no such rectification having adverse effect upon an assessee shall be made unless the assessee have been given a reasonable opportunity of being heard. (2) Where any such rectification has the effect of reducing the assessment, the assessing authority shall order any refund which may be due to such person. (3) Where any such rectification has the effect of enhancing the assessment or reducing the refund, the assessing authority shall serve on the person a notice of demand in the prescribed form specifying the sum payable, and such notice of demand shall be deemed to be issued under section 18 and the provisions of this Act shall apply accordingly.