(1)Where by any provision of this or any subsequent Act any change is made in the classes of goods which are chargeable goods or in the rate at which tax is chargeable in respect of goods of any class, section twenty-eight of the Finance (No. 2) Act, 1946 (which provides for adjustments of rights between buyer and seller) shall apply as if the change had been effected by an order of the Treasury and as if the references to the approval of the order by the Commons House of Parliament were references to the passing of the Act which makes the change.
(2)The said section twenty-eight shall apply in relation to the application of a chargeable process under any contract not being a purchase, as if—
(a)the contract were a purchase ; and
(b)the goods resulting from the application of the process had been bought under the contract ; and
(c)references in the said section twenty-eight to the buyer and the seller were respectively references to the party to whose order the process is applied under the contract and the party who applies the process to his order thereunder,
so, however, that in considering whether any and, if so, what sum is recoverable under subsection (1) of that section in the case of such a contract, only tax chargeable on the completion of the process for which the party who is to be treated under this subsection as the seller is accountable shall be taken into account.
(3)The said section twenty-eight shall apply and be deemed always to have applied in relation "to—
(a)the provisions of this, Act rendering purchase tax chargeable on the completion of any chargeable process ; and
(b)any order under this Act varying the Fourth Schedule to this Act ; and
(c)any provisions of any Act subsequent to this Act varying the said Schedule,
as if the said provisions of this Act, the said order or the said provisions of the subsequent Act were making a change in the classes of goods which were chargeable goods.