4.—(1) For the purposes of article 3, the applicable turnover of a large retailer is the sum of—
(a)all amounts derived by the large retailer from the provision of goods and services falling within the large retailer’s ordinary activities in the United Kingdom; and
(b)all other amounts received by the large retailer in the course of the large retailer’s ordinary activities in the United Kingdom by way of gift, grant, subsidy or membership fee,
after deduction of trade discounts, value added tax and other taxes based on the amounts so derived or received.
(2) Amounts are to be calculated in conformity with generally accepted accounting principles and practices.