(1)The amount of input tax for which a taxable person is entitled to credit at the end of any period shall be so much of the input tax for the period (that is input tax on supplies, acquisitions and importations in the period) as is allowable by or under regulations as being attributable to supplies within subsection (2) below.
(2)The supplies within this subsection are the following supplies made or to be made by the taxable person in the course or furtherance of his business—
(a)taxable supplies;
(b)supplies outside the United Kingdom which would be taxable supplies if made in the United Kingdom;
(c)such other supplies outside the United Kingdom and such exempt supplies as the Treasury may by order specify for the purposes of this subsection.
(3)The Commissioners shall make regulations for securing a fair and reasonable attribution of input tax to supplies within subsection (2) above, and any such regulations may provide for—
(a)determining a proportion by reference to which input tax for any prescribed accounting period is to be provisionally attributed to those supplies;
(b)adjusting, in accordance with a proportion determined in like manner for any longer period comprising two or more prescribed accounting periods or parts thereof, the provisional attribution for any of those periods;
(c)the making of payments in respect of input tax, by the Commissioners to a taxable person (or a person who has been a taxable person) or by a taxable person (or a person who has been a taxable person) to the Commissioners, in cases where events prove inaccurate an estimate on the basis of which an attribution was made; and
(d)preventing input tax on a supply which, under or by virtue of any provision of this Act, a person makes to himself from being allowable as attributable to that supply.
(4)Regulations under subsection (3) above may make different provision for different circumstances and, in particular (but without prejudice to the generality of that subsection) for different descriptions of goods or services; and may contain such incidental and supplementary provisions as appear to the Commissioners necessary or expedient.