and (b) of section 52). For purposes of the preceding sentence, in applying sections 267(b) and 707(b)(1), 10 percent shall be substituted for 50 percent each place it appears. (3) Transportation outside the United States In the case an amount paid for transportation any portion of which is outside the United States, the portion of such amount paid which is allocable to transportation within the United States shall be determined under regulations prescribed by the Secretary. Such regulations shall include rules to include transportation outside the United States the primary purpose of which is to avoid the tax imposed by this section. (e) Exemption for United States and possessions and State and local governments The tax imposed by subsection (a) shall not apply to amounts paid for transportation of property purchased for the exclusive use of the United States, or any State or political subdivision thereof. . (b) Credits or refunds to persons who collected certain taxes Section 6415 of such Code is amended by striking or 4271 each place it appears and inserting 4271, or 4286 . (c) Clerical amendment The table of subchapters for chapter 33 of the Internal Revenue Code of 1986 is amended by inserting after the item relating to subchapter C the following new item: Subchapter D. Ground Transportation Freight Tax . (d) Regulations Not later than 180 days after the date of the enactment of this Act, the Secretary of the Treasury shall issue regulations to carry out the amendments made by this section. (e) Effective date The amendments made by this section shall apply to transportation beginning on or after the last day of the 180-day period beginning on the date of the issuance of regulations under subsection (c).