4 Further provisions relating to apportionments and contributions
1 Paragraph (2) applies if relevant expenditure is incurred on a dwelling-house which—
(a) is owned jointly or in common by the person entitled to the deduction and by other persons, or
(b) is subject to differing estates or interests.
2 If this paragraph applies—
(a) a just and reasonable apportionment of the relevant expenditure must be made, and
(b) the deduction allowed is the part of the relevant expenditure incurred by the person entitled to the deduction.
3 Paragraph (4) applies if relevant expenditure is incurred which—
(a) falls within paragraph (1), and
(b) exceeds the maximum amount (see regulation 3).
4 If this paragraph applies—
(a) the relevant expenditure must be restricted on a proportionate basis to arrive at the maximum amount,
(b) a just and reasonable apportionment of the maximum amount must be made, and
(c) the deduction allowed is the part of the maximum amount incurred by the person entitled to the deduction.
5 If the person entitled to the deduction has received a contribution from any other person towards the relevant expenditure incurred, that contribution shall be excluded in calculating the relevant expenditure incurred by the person entitled to the deduction.
6 If in connection with this regulation any question arises as to the amount of the deduction to which a person may be entitled—
(a) the amount shall be treated as if it were an amount specified in a paragraph of subsection (1) of section 42 of the Income and Corporation Taxes Act 1988 (appeals against determinations under sections 34 to 36 or Chapter 4 of Part 3 of ITTOIA 2005), and
1988 c. 1; section 42 was amended by paragraph 24 of Schedule 1 to the Income Tax (Trading and Other Income) Act 2005.
(b) the procedure set out in that section shall apply accordingly.