(1)References in section 4 to income tax chargeable at the higher rate include references to tax chargeable by virtue of section 353(4), 369(3A), 683(1) or 684(1) of the Taxes Act (restriction to basic rate of relief on certain interest etc. and settlements) in respect of excess liability (that is, liability to income tax over what it would be if all income tax were charged at the basic rate to the exclusion of any higher rate); and
(a)where for any year of assessment a deduction is by virtue of section 353(4) or 369(3A) not allowed in computing the total income of a person for the purposes of excess liability then, whether or not he is chargeable to tax otherwise than at the basic rate, that deduction shall not be allowed for the purposes of section 4(4);
(b)where for any year of assessment income is treated by virtue of section 683(1) or 684(1) as the income of a person for the purposes of excess liability then, whether or not he is chargeable to tax otherwise than at the basic rate, it shall also be treated as his income for the purposes of section 4(4).
(2)Where for any year of assessment—
(a)by virtue of section 549(2) of the Taxes Act (gains under life policy or life annuity contract) a deduction of an amount is made from a person’s total income for the purposes of excess liability, or
(b)by virtue of section 683(1) or 684(1) of that Act an amount of a person’s income is treated as not being his income for those purposes, or
(c)by virtue of section 699(1) of that Act (income accruing before death) the residuary income of an estate is treated as reduced so as to reduce a person’s income by any amount for those purposes,
section 4(4) shall have effect as if his income for the year were reduced by that amount.
(3)Where by virtue of section 547(1)(a) of the Taxes Act (gains from insurance policies etc.) a person’s total income for a year of assessment is deemed to include any amount or amounts—
(a)section 4(4) shall have effect as if his total income included not the whole of the amount or amounts concerned but only the appropriate fraction within the meaning of section 550(3) of that Act, and
(b)if relief is given under section 550 of that Act and the calculation required by section 550(2)(b) does not involve the higher rate of income tax, section 4(2) and (3) shall have effect as if no income tax were chargeable at the higher rate in respect of his income.
(4)Nothing in subsection (1) above shall be taken to reduce, and nothing in subsections (2) and (3) above shall be taken to increase, the amount of the deduction which a person is entitled to make from his total income by virtue of any provision of Chapter I of Part VII of the Taxes Act which limits any allowance by reference to the level of his total income.