TRANSPORTATION AND COMMUNICATION 423 and be made in such manner as the Commissioner with the approval of the Secretary may by regulation prescribe. The Commissioner may extend the time for making returns and paying the taxes col- lected, under such rules and regulations as he shall prescribe with the approval of the Secretary, but no such extension shall be for more than 90 days. SEC. 3468. CROSS REFERENCE. For enforcement of liability for taxes collected, see section 3661. SUBCHAPTER C-ADMINISTRATIVE PROVISIONS SEC. 3470. PAYMENT OF TAXES. The taxes imposed by this chapter shall, without assessment by the Commissioner or notice from the collector, be due and payable to the collector at the time fixed for filing the return. If the tax is not paid when due, there shall be added as part of the tax interest at the rate of 6 per centum per annum from the time the tax became due until paid. SEC. 3471. REFUNDS AND CREDITS. (a) Credit or refund of any overpayment of tax imposed by sub- chapter B may be allowed to the person who collected the tax and paid it to the United States if such person establishes, to the satis- faction of the Commissioner, under such regulations as the Commis- sioner with the approval of the Secretary may prescribe, that he has repaid the amount of such tax to the person from whom he collected it, or obtained the consent of such person to the allowance of such credit or refund. (b) Any person entitled to refund of tax under this chapter paid, or collected and paid, to the United States by him may take credit therefor against taxes due upon any monthly return. (c) Any person making a refund of any payment on which tax under subchapter B has been collected, may repay therewith the amount of tax collected on such payment, and the amount of tax so repaid may be credited against the tax under any subsequent return. SEC. 3472. REGULATIONS. The Commissioner, with the approval of the Secretary, shall prescribe and publish all needful rules and regulations for the en- forcement of subchapters A and B of this chapter. SEC. 3473. APPLICABILITY OF ADMINISTRATIVE PROVISIONS. All provisions of law (including penalties) applicable in respect of the taxes imposed by section 1700, shall, in so far as applicable and not inconsistent with this chapter, be applicable in respect of the taxes imposed by this chapter. SEC. 3474. EFFECTIVE DATE OF CHAPTER. This chapter shall take effect on the first day of that calendar month occurring next after the enactment of this title.