(1) References in this Part to capital expenditure and capital sums -

(a) in relation to the person incurring the expenditure or paying the sums, do not include any expenditure or sum allowed to be deducted in computing for the purposes of tax the profits or gains of a trade, profession, office or employment carried on or held by that person, and

(b) in relation to the person receiving the amounts expended or the sums in question, do not include references to any amounts or sums which are to be taken into account as receipts in computing the profits or gains of any trade, profession, office or employment carried on or held by that person,

and do not include, in relation to any person referred to in paragraphs (a) and (b), any expenditure or sum in the case of which a deduction of tax is to be or may be made under section 237 or 238.

(2) Any reference in this Part to the date on which expenditure is incurred shall be construed as a reference to the date when the sums in question become payable; but, for the purposes of section 284, this subsection shall apply only in respect of machinery and plant provided for use for the purposes of a trade on or after the 6th day of April 1996.

(2A) For the purposes only of determining, in relation to a claim for an allowance under Chapter 1 of this Part, whether and to what extent capital expenditure incurred on the construction (within the meaning of section 270) of: