law: 23. Assessment.
  (1) The amount of tax due from a registered dealer shall be assessed separately for each year during which he is liable to pay the tax:
  Provided that when such dealer fails to furnish a return relating to any period of a year by the prescribed date, the Commissioner may, if he thinks fit, assess the tax due from such dealer separately for that period or any other period of such year:
  Provided further that the Commissioner may, subject to such conditions as may be prescribed and for reasons to be recorded in writing, assess the tax due from any dealer for a part of a year.
  (2) If the Commissioner is satisfied that the returns furnished in respect of any period are correct and complete, he shall assess the amount of tax due from the dealer on the basis of such returns.
  (3) (a) If the Commissioner is not satisfied that the returns furnished in respect of any period are correct and complete and he thinks it necessary to require the presence of the dealer or the production of further evidence, he shall serve on such dealer in the prescribed manner a notice requiring him on a date and at a place specified therein either to attend and produce or cause to be produced all evidence on which such dealer relies in support of his returns, or to produce such evidence as is specified in the notice.
  (b) On the date specified in the notice, or as soon as may be thereafter, the Commissioner shall, after considering all the evidence which may be produced, assess the amount of tax due from the dealer.
  (4) If a dealer fails to comply with the terms of any notice issued under sub-section (3), the Commissioner shall assess to the best of his judgment the amount of tax, if any, due from him.
  (5) If a dealer fails to furnish returns in respect of any period by the prescribed date, the Commissioner shall, after giving the dealer a reasonable opportunity of being heard, assess to the best of his judgment the amount of tax, if any, due from him.
  (6) If, upon information which has come into his possession, the Commissioner is satisfied that any dealer who has been liable to pay tax under this Act in respect of any period, has failed to get himself registered under section 14 or section 17, as the case may be, the Commissioner shall proceed in such manner as may be prescribed to assess to the best of his judgment the amount of tax due from the dealer in respect of such period and all subsequent periods and in making such assessment shall give the dealer a reasonable opportunity of being heard, and the Commissioner may, if he is satisfied that the default was made without reasonable cause, direct that the dealer shall pay, by way of penalty, in addition to the amount of the tax so assessed, a sum not exceeding twice that amount.
  (7) No assessment under the provisions of sub-sections (1) to (5) shall be made after the expiry of four years, and no assessment under the provisions of sub-section (6) shall be made after the expiry of six years from the end of the year in respect of which or part of which the tax is assessable:
  Provided that where such assessment is made in consequence of or to give effect to, any order of an appellate or revisional authority or of a court, the period of four years or six years, as the case may be, shall be reckoned from the date of such order and further that the provisions of sub-section (1) of section 24 regarding time limit for service of notice shall not apply for assessment made under this proviso.
  (8) Any assessment made under this section shall be without prejudice to any prosecution for an offence under this Act.