the expenditure actually incurred on the construction of the building or structure shall be left out of account for the purposes of sections 1 to 8, but

subject to subsection (2) below, the person who buys that interest shall be deemed for those purposes to have incurred, on the date when the purchase price becomes payable, expenditure on the construction of the building or structure equal to that actual expenditure or to the net price paid by him for that interest, whichever is the less.

if that sale is the only sale of the relevant interest before the building or structure is used, paragraph (b) shall have effect as if the words “that actual expenditure or to” and “whichever is the less” were omitted; and

in any other case, paragraph (b) shall have effect as if the reference to the expenditure actually incurred on the construction of the building or structure were a reference to the price paid on that sale.

expenditure is incurred on the construction of a building or structure by a person carrying on a trade which consists, in whole or in part, in the construction of buildings or structures with a view to their sale, and

after the building or structure has been used, he sells the relevant interest in it in the course of that trade or, as the case may be, of that part of that trade, and

the purchase price payable on the sale becomes payable on or after 27th July 1989.

the original expenditure had been capital expenditure,

all appropriate writing-down allowances had been made to the person incurring it, and

all appropriate balancing allowances or charges had been made on the occasion of the sale.