101(1)Sub-paragraph (2) applies if—
(a)a person is entitled to a writing-down allowance or a balancing allowance or liable to a balancing charge in respect of qualifying expenditure, and
(b)the trade use condition is met.
(2)The allowance or charge is to be given effect in calculating the profits of that person’s trade, by treating—
(a)the allowance as an expense of the trade, and
(b)the charge as a receipt of the trade.
(3)Sub-paragraph (4) applies if—
(a)a person is entitled to a writing-down allowance or a balancing allowance or liable to a balancing charge in respect of qualifying expenditure, and
(b)the trade use condition is not met.
(4)Sections 479 and 480 apply in relation to giving effect to the allowance or charge referred to in sub-paragraph (3) as they apply in relation to giving effect to an allowance or charge under Chapter 3 of Part 8 in respect of qualifying non-trade expenditure.
(5)For the purposes of Part 8 a person’s “income from patents” includes balancing charges to which the person is liable in respect of qualifying expenditure.