(1) (a) Subject to the provisions of sections 16 and 17, tax on sale of goods (other than goods specified in Schedule IV) shall be levied at each point in a series of sales in the State of Bihar by a dealer liable to pay tax under this Act.
         (b) Where the tax is levied at each point of sale, the tax payable by a dealer at any point shall be the amount arrived at after deducting, the input tax credit specified under section 16 or section 17, from the tax computed at that point of sale.
         (2) (a) The tax on sales, in respect of goods specified in Schedule IV, shall be levied at the first point of their sale in the State of Bihar by a dealer and subsequent sales of the same goods in the State of Bihar shall not be levied to tax, if the dealer making the subsequent sale produces before the prescribed authority the original copy of the cash memo, or invoice or bill issued to him and files a true and complete declaration in the form and in the manner prescribed.
         (b) The declaration referred to in clause (a) shall be issued by the selling dealer to the purchasing dealer not later than the 30th day of September of the year following the year to which such sales relate.
     (3) If upon information, the prescribed authority has reasons to believe that the selling dealer has, without reasonable cause, failed to issue to the purchasing dealer the declaration referred to in sub-section (2), he shall, after giving the selling dealer a reasonable opportunity of being heard, direct that the selling dealer shall pay, by way of penalty, a sum of rupees five thousand per month for every month of default or the amount of tax involved, whichever is less.