7(1)The amount of the anti-forestalling charge on a chargeable pre-change supply is the amount of VAT that would be chargeable on the supply if it were subject to VAT at 20%.U.K.
This is subject to any reduction under sub-paragraph (2).
(2)If the chargeable pre-change supply is not wholly linked to the post-change period, the anti-forestalling charge is the relevant proportion of that amount.
(3)The relevant proportion is—
where—
P is so much of the consideration for the chargeable supply as is attributable, on a just and reasonable basis, to that part of the supply (or, in the case of a grant of a right, that part of the supply to which the right relates) which is linked to the post-change period;
W is the whole of the consideration for the chargeable pre-change supply.