(1) The small and micro business regulations may make provision -

(a) about the calculation of the headcount of staff, turnover and balance sheet total of an undertaking, including provision about the period ("assessment period") in respect of which they are to be calculated;

(b) for the headcount of staff, turnover and balance sheet total, or a proportion of such, of any undertaking which satisfies such conditions as may be prescribed in relation to another undertaking (the "principal undertaking") to be treated as part of the principal undertaking's headcount of staff, turnover and balance sheet total.

(2) Conditions which may be prescribed under subsection (1)(b) include, in particular, conditions relating to -

(a) the extent of ownership (whether direct or indirect) of one undertaking by one or more other undertakings;

(b) the degree of control exercised (whether directly or indirectly) by one or more undertakings over another.

(3) The small and micro business regulations may make provision about -

(a) the assessment period or periods in respect of which an undertaking must meet the small business size conditions or the micro business size conditions in order to be a small business or (as the case may be) micro business;