(5) If, within 14 days after the time applicable under subsection (2) or (3) above, the person making the supply issues a VAT invoice in respect of it, then, unless he has notified the Commissioners in writing that he elects not to avail himself of this subsection, the supply shall (to the extent that it is not treated as taking place at the time mentioned in subsection (4) above) be treated as taking place at the time the invoice is issued.
(6) The Commissioners may, at the request of a taxable person, direct that subsection (5) above shall apply in relation to supplies made by him (or such supplies made by him as may be specified in the direction) as if for the period of 14 days there were substituted such longer period as may be specified in the direction.
(7) Where any supply of goods involves both—
(a) the removal of the goods from the United Kingdom; and
(b) their acquisition in another member State by a person who is liable for VAT on the acquisition in accordance with provisions of the law of that member State corresponding, in relation to that member State, to the provisions of section 10,
subsections (2), (4) to (6) and (10) to (12) of this section shall not apply and the supply shall be treated for the purposes of this Act as taking place on whichever is the earlier of the days specified in subsection (8) below.
(8) The days mentioned in subsection (7) above are—
(a) the 15th day of the month following that in which the removal in question takes place; and
(b) the day of the issue, in respect of the supply, of a VAT invoice or of an invoice of such other description as the Commissioners may by regulations prescribe.
(9) . . .
(10) The Commissioners may, at the request of a taxable person, by direction alter the time at which supplies made by him (or such supplies made by him as may be specified in the direction) are to be treated as taking place, either—
(a) by directing those supplies to be treated as taking place—
(i) at times or on dates determined by or by reference to the occurrence of some event described in the direction; or
(ii) at times or on dates determined by or by reference to the time when some event so described would in the ordinary course of events occur,
the resulting times or dates being in every case earlier than would otherwise apply; or
(b) by directing that, notwithstanding subsections (5) and (6) above, those supplies shall (to the extent that they are not treated as taking place at the time mentioned in subsection (4) above) be treated as taking place—
(i) at the beginning of the relevant working period (as defined in his case in and for the purposes of the direction); or
(ii) at the end of the relevant working period (as so defined).
(11) Where goods are treated as supplied by an order under section 5(5), the supply is treated as taking place when they are appropriated to the use mentioned in that section.
(12) Where there is a supply of goods by virtue only of paragraph 5(1) of Schedule 4, the supply is treated as taking place when the goods are transferred or disposed of as mentioned in that paragraph.
(13) Where there is a supply of services by virtue only of paragraph 5(4) of Schedule 4, the supply is treated as taking place when the goods are appropriated to the use mentioned in that paragraph.
(14) The Commissioners may by regulations make provision with respect to the time at which (notwithstanding subsections (2) to (8) and (11) to (13) above or section 55(4)) a supply is to be treated as taking place in cases where—
(a) it is a supply of goods or services for a consideration the whole or part of which is determined or payable periodically, or from time to time, or at the end of any period, or
(b) it is a supply of goods for a consideration the whole or part of which is determined at the time when the goods are appropriated for any purpose, or
(c) there is a supply to which section 55 applies, or
(d) there is a supply of services by virtue of paragraph 5(4) of Schedule 4 or an order under section 5(4);
and for any such case as is mentioned in this subsection the regulations may provide for goods or services to be treated as separately and successively supplied at prescribed times or intervals.
[(14A) . . . this section and any regulations under this section or section 8(4) shall have effect subject to section 97A.]