417Determination of entitlement or liability
(1)Whether a person who has incurred qualifying expenditure is entitled to a writing-down allowance or a balancing allowance, or liable to a balancing charge, for a chargeable period depends on—
(a)how much of the expenditure is unrelieved qualifying expenditure for that period (“UQE”), and
(b)the total of any disposal receipts to be brought into account for that period (“TDR”) by reference to the expenditure.
(2)If UQE exceeds TDR, the person is entitled to a writing-down allowance or a balancing allowance for the period.
(3)If TDR exceeds UQE, the person is liable to a balancing charge for the period.
(4)The entitlement under subsection (2) is to a writing-down allowance except in cases for which sections 426 to 431 provide for the entitlement to be to a balancing allowance.