s 334 Writing off writing-down allowances
(1) If a writing-down allowance is made in respect of the qualifying expenditure, the amount of the allowance is written off at the end of the chargeable period for which the allowance is made. (2) If a balancing event occurs at the end of the chargeable period referred to in subsection (1), the amount written off under that subsection is to be taken into account in calculating the residue of qualifying expenditure immediately before the event to determine what balancing adjustment (if any) is to be made.