18.—(1) The income of a relevant person shall be determined on a weekly basis by aggregating—
(a)his average weekly earnings from employment as an employed earner, determined in accordance with this Chapter and Chapter VI of this Part,
(b)his average weekly earnings from employment as a self-employed earner, determined in accordance with this Chapter and Chapter VII of this Part,
(c)his average weekly income other than earnings, determined in accordance with this Chapter and Chapter VIII of this Part,
(d)the weekly tariff income determined under regulation 40 (determination of tariff income from capital), and
by then deducting the average weekly relevant child care charge, determined in accordance with regulation 19 (treatment of child care charges), up to a maximum deduction in respect of the relevant person’s family of £60 per week.
(2) For the purposes of paragraph (1) “income” includes income to which regulations 30 (annuity treated as income), 31 (notional income), 43 (determination of grant income) and 46 (treatment of student loans) refer.