s 475 Unrelieved qualifying expenditure
(1) A person has unrelieved qualifying expenditure to carry forward from a chargeable period if for that period AQE exceeds TDR. (2) The amount of the unrelieved qualifying expenditure is— (a) the excess less the writing-down allowance made for the period, or (b) if no writing-down allowance is claimed for the period, the excess. (3) No amount may be carried forward as unrelieved qualifying expenditure from the final chargeable period.