Section 284 - Tax imposed1. There is hereby levied and imposed an excise tax of four cents per gallon upon motor fuel (a) imported into or caused to be imported into the state by a distributor for use, distribution, storage or sale in the state or upon motor fuel which is produced, refined, manufactured or compounded by a distributor in the state (which acts shall hereinafter in this subdivision be encompassed by the phrase "imported or manufactured") or (b) if the tax has not been imposed prior to its sale in this state, which is sold by a distributor (which act, in conjunction with the acts described in paragraph (a) of this subdivision, shall hereinafter in this article be encompassed by the phrase "imported, manufactured or sold"), except when imported, manufactured or sold under circumstances which preclude the collection of such tax by reason of the United States constitution and of laws of the United States enacted pursuant thereto or when imported or manufactured by an organization described in paragraph one or two of subdivision (a) of section eleven hundred sixteen of this chapter or a hospital included in the organizations described in paragraph four of such subdivision for its own use or consumption and except kero-jet fuel when imported or manufactured by an airline for use in its airplanes. Provided, further, no motor fuel shall be included in the measure of the tax unless it shall have previously come to rest within the meaning of federal decisional law interpreting the United States constitution. All tax for the period for which a return is required to be filed shall be due on the date limited for the filing of the return for such period, regardless of whether a return is filed by such distributor as required by this article or whether the return which is filed correctly shows the amount of tax due.2. If, prior to April first, nineteen hundred forty-seven, a contract of sale of motor fuel shall have been made, and delivery thereof pursuant to such contract is made within the state thereafter, from a stock of motor fuel which, at the time of the taking of such fuel therefrom for such delivery, is subject to the taxing power of the state, the vendor shall be deemed a distributor, for the purposes of this article, and such motor fuel shall be deemed to be sold, and shall be subject to such tax, at the time of such delivery.