5.—(1) Subject to sub-paragraphs (2) and (3)—
(a)where a person has been a self-employed earner for 52 weeks or more including the relevant week, the amount of his earnings shall be determined by reference to the average of the earnings which he has received in the 52 weeks ending with the relevant week;
(b)where the person has been a self-employed earner for a period of less than 52 weeks including the relevant week, the amount of his earnings shall be determined by reference to the average of the earnings which he has received during that period.
(2) Where a person who is a self-employed earner provides in respect of the employment a profit and loss account and, where appropriate, a trading account or a balance sheet or both, and the profit and loss account is in respect of a period at least 6 months but not exceeding 15 months and that period terminates within the 12 months immediately preceding the effective date, the amount of his earnings shall be determined by reference to the average of the earnings over the period to which the profit and loss account relates and such earnings shall include receipts relevant to that period (whether or not received in that period).
(3) Where a calculation would, but for this sub-paragraph, produce an amount which, in the opinion of the child support officer, does not accurately reflect the normal amount of the earnings of the person in question, such earnings, or any part of them, shall be calculated by reference to such other period as may, in the particular case, enable the normal weekly earnings of that person to be determined more accurately and for this purpose the child support officer shall have regard to—
(a)the earnings received, or due to be received, from any employment in which the person in question is engaged, or has been engaged or is due to be engaged;
(b)the duration and pattern, or the expected duration and pattern, of any employment of that person.
(4) In sub-paragraph (2)—
(a)“balance sheet” means a statement of the financial position of the employment disclosing its assets, liabilities and capital at the end of the period in question;
(b)“profit and loss account” means a financial statement showing net profit or loss of the employment for the period in question; and
(c)“trading account” means a financial statement showing the revenue from sales, the cost of those sales and the gross profit arising during the period in question.