(1) Where an assessment or re-assessment of a dealer has been made under this Act or the Act repealed by this Act and for any reason any sale or purchase of goods liable to tax under this Act or the Act repealed by this Act during any period,-

(a) has been under-assessed or has escaped assessment, or

(b) has been assessed at a lower rate, or

(c) any wrong deduction has been made while making the assessment, or

(d) a rebate of input tax has incorrectly been allowed while making the assessment,

(e) is rendered erroneous and prejudicial to the interest of revenue consequent to or in the light of any judgment or order of any Court or Tribunal, which has become final,

the Commissioner may, at any time within a period of five calendar years from the date of order of assessment or from the date of judgment or order of any Court or Tribunal, proceed in such manner as may be prescribed, to assess or re-assess, as the case may be the tax payable by such dealer after making such enquiry as he considers necessary, and assess or re-assess to tax.

(2) The Commissioner shall, where the omission leading to assessment or re-assessment made under sub-section (1) is attributable to the dealer,in addition to interest at the rate specified in sub-clause (iii) of clause (a) of sub-section (4) of Section 19, impose upon him a penalty not exceeding twice the amount of tax so assessed or re-assessed but not less than one and half times of the amount of tax assessed.

(3) The assessment or re-assessment under sub-section (1) shall be made within a period of two calendar years from the date of commencement of the proceedings under the said sub-section.