If a gain to which section 222 applies accrues on the disposal of a dwelling-house or part of a dwelling-house part of which is used exclusively for the purpose of a trade or business, or of a profession or vocation, the gain shall be apportioned and sections 223 and 223B shall apply in relation to the part of the gain apportioned to the part which is not exclusively used for those purposes.
If at any time in the period of ownership there is a change in what is occupied as the individual's residence, whether on account of a reconstruction or conversion of a building or for any other reason, or there have been changes as regards the use of part of the dwelling-house for the purpose of a trade or business, or of a profession or vocation, or for any other purpose, the relief given by sections 223 and 223B may be adjusted in a manner which is just and reasonable.
Sections 223 and 223B shall not apply in relation to a gain if the acquisition of, or of the interest in, the dwelling-house or the part of a dwelling-house was made wholly or partly for the purpose of realising a gain from the disposal of it, and shall not apply in relation to a gain so far as attributable to any expenditure which was incurred after the beginning of the period of ownership and was incurred wholly or partly for the purpose of realising a gain from the disposal.
This section is subject to section 225D (private residence of adult placement carer).