5.—(1) This paragraph applies to income from a business carried on by the qualifying person (whether or not with any other person).
(2) The amount to be taken into account as the qualifying person’s annual income from the business is an amount which, having regard to the latest available information, fairly represents the current annual net profit of the business or, if the qualifying person shares the net profit with any other person, his share of the net profit.
(3) In this paragraph “business” includes any trade, profession or vocation.