99(1)A person is entitled to a balancing allowance for a chargeable period in respect of qualifying expenditure if there is unrelieved qualifying expenditure for that period and any of the following occur in that period—
(a)the patent rights come to an end without subsequently being revived, or
(b)the person sells all of those rights, or so much of them as that person still owned at the beginning of the period.
This is subject to sub-paragraph (2).
(2)The person is not entitled to a balancing allowance unless—
(a)a writing-down allowance has been given in respect of the expenditure, or
(b)a writing-down allowance could, but for the rights coming to an end or being sold, have been given in respect of the expenditure.
(3)The amount of the balancing allowance is—
(a)in the case of a sale, equal to the unrelieved qualifying expenditure for the chargeable period, less the net proceeds of sales taking place in the chargeable period (so far as they consist of capital sums), and
(b)in any other case, equal to the unrelieved qualifying expenditure for the chargeable period.