proviso to sub rule (1) of rule 8 and by subrule (ii) of that rule the lump sum fixed by the State Government as payable in lieu of the tax on fare or freight, as the case may be, shall be deposited in cash into a Government Treasury or a Sub Treasury in equal quarterly instalments payable within 15 days from the 31st day of March, the 30th day of June, the 30th day of September and the 31st day of December every year; and in case of such vehicles not registered in Rajasthan to the incharge of the check post or barrier at the time of their entry into the State of Rajasthan or to the officer of the Excise and Taxation Department nearest to the point of 523 entry into the State and having jurisdiction over that area: Provided that Provided that (a) for the quarter ending on the 30th day of June ', 1959, such payment shall be made for the months of May and June, 1959, at the rate of 1/12 of the said sum for each month, (b) where the owner has not plied his vehicle for the entire quarter immediately preceding any of the aforesaid dates a proportionate decrease in the amount due for that quarter may be made, (c) if the owner ceases to ply his vehicle on a date preceding any of the aforesaid dates, the proportionate amount for the quarter shall be paid by him immediately upon such cessation, and (d) where the owner has not plied his vehicle for a continuous period of not less than three months and produces a certificate from the authority competent under the Rajasthan Motor Vehicles Taxation Act, 1951, or the rules made thereunder to the effect that he has been refunded the tax for that period under section 7 of the said Act, no amount by way of tax under the Act shall be payable for such period.