26 U.S.C. § 5732: Payment of tax

(a) Condition precedent to carrying on businessNo person shall be engaged in or carry on any trade or business subject to tax under this subchapter until he has paid the special tax therefor. (b) ComputationAll special taxes under this subchapter shall be imposed as of on the first day of July in each year, or on commencing any trade or business on which such tax is imposed. In the former case the tax shall be reckoned for 1 year, and in the latter case it shall be reckoned proportionately, from the first day of the month in which the liability to a special tax commenced, to and including the 30th day of June following. (c) How paid(1) Payment by returnThe special taxes imposed by this subchapter shall be paid on the basis of a return under such regulations as the Secretary shall prescribe. (2) Stamp denoting payment of taxAfter receiving a properly executed return and remittance of any special tax imposed by this subchapter, the Secretary shall issue to the taxpayer an appropriate stamp as a receipt denoting payment of the tax. This paragraph shall not apply in the case of a return covering liability for a past period.