(1) Part 8 of the Principal Act is amended -

(a) in section 256(1) by substituting the following for the definition of "appropriate tax":

"'appropriate tax', in relation to a payment of relevant interest, means -

(a) as respects the year of assessment 2017, a sum representing income tax on the amount of the payment at the rate of 39 per cent,

(b) as respects the year of assessment 2018, a sum representing income tax on the amount of the payment at the rate of 37 per cent,

(c) as respects the year of assessment 2019, a sum representing income tax on the amount of the payment at the rate of 35 per cent, and

(d) as respects the year of assessment 2020 and each subsequent year of assessment, a sum representing income tax on the amount of the payment at the rate of 33 per cent;",

and

(b) in section 267M by substituting the following for subsection (2):

"(2)

(a) Notwithstanding section 15 and subject to paragraph (aa), where the taxable income of an individual includes -