(1) Subject to [sections 18 and 18B]¹ and any regulations under subsection (3) below, where goods are acquired from another member State, the acquisition shall be treated for the purposes of this Act as taking place on whichever is the earlier of—

(a) the 15th day of the month following that in which the event occurs which, in relation to that acquisition, is the first relevant event for the purposes of taxing the acquisition; and

(b) the day of the issue, in respect of the transaction in pursuance of which the goods are acquired, of an invoice of such a description as the Commissioners may by regulations prescribe.

(2) For the purposes of this Act the event which, in relation to any acquisition of goods from another member State, is the first relevant event for the purposes of taxing the acquisition is the first removal of the goods which is involved in the transaction in pursuance of which they are acquired.

(3) The Commissioners may by regulations make provision with respect to the time at which an acquisition is to be treated as taking place in prescribed cases where the whole or part of any consideration comprised in the transaction in pursuance of which the goods are acquired is determined or payable periodically, or from time to time, or at the end of a period; and any such regulations may provide, in relation to any case to which they apply, for goods to be treated as separately and successively acquired at prescribed times or intervals.