“Qualifying trade expenditure” means capital expenditure incurred by a person on the purchase of patent rights for the purposes of a trade within the charge to tax carried on by the person.

The same expenditure may not be taken into account as qualifying trade expenditure in relation to more than one trade.

Expenditure incurred for the purposes of a trade by a person about to carry on the trade is to be treated as if it had been incurred by him on the first day on which he carries on the trade.

But subsection (3) does not apply if the person has before that day sold all the rights on the purchase of which the expenditure was incurred.