4A. Point or points in a series of sales at which duty shall levied

(1)Subject to the provisions of sub-section (2), the duty under the Act shall be levied at each point in a series of sales of energy in the Stat of Bihar. (2) The amount of duty paid at each preceding stage of sale shall be adjusted against the amount of duty payable at each subsequent stage of sale in the manner prescribed. Provided that if the sale of energy at any subsequent points is not leviable to duty under sub-section (2) of section 3, the liability, in respect of any subsequent period, of the preceding seller shall stand reduced, in the manner prescribed, to the extent of the duty paid by him in respect of such subsequent sale of energy as is not leviable to duty under sub-section (2) of section3.