(1) Subject to subsection (2), in the case of a relevant residential property -
(a) which is occupied by a liable person as his or her sole or main residence, and
(b) which is subject to a mortgage,
the gross income amounts referred to in section 132 may be increased by an amount which is 80 per cent of the amount of the mortgage interest payments that, as far as can reasonably be foreseen at the liability date in the relevant year, will be made before the end of the relevant year, by such a person in respect of the relevant residential property.
(2) Subsection (1) shall apply in respect of a relevant residential property for a relevant year commencing after 31 December 2020 only where that subsection applied in respect of the relevant residential property for a relevant year commencing before that date.