15Class 4 contributions recoverable under the Income Tax Acts
(1)Class 4 contributions shall be payable for any tax year in respect of all annual profits or gains which—
(a)are immediately derived from the carrying on or exercise of one or more trades, professions or vocations, and
(b)are profits or gains chargeable to income tax under Case I or Case II of Schedule D for the year of assessment corresponding to that tax year.
(2)Class 4 contributions in respect of profits or gains shall be payable—
(a)in the same manner as any income tax which is, or would be, chargeable in respect of those profits or gains (whether or not income tax in fact falls to be paid), and
(b)by the person on whom the income tax is (or would be) charged,
in accordance with assessments made from time to time under the Income Tax Acts as applied and modified by section 16(1) to (3) of the Great Britain Contributions and Benefits Act.
(3)A Class 4 contribution for any tax year shall be an amount equal to 6.3 per cent. of so much of the profits or gains referred to in subsection (1) above (as computed in accordance with Schedule 2 to the Great Britain Contributions and Benefits Act, the text of which is set out as Schedule 2 to this Act) as exceeds £6,120 and does not exceed £21,060.
(4)The reference in subsection (1) above to profits or gains chargeable to income tax under Case I or Case II of Schedule D shall be taken to include a reference to profits or gains consisting of a payment of enterprise allowance chargeable to income tax under Case VI of Schedule D by virtue of section 127(2) of the [1988 c. 1.] Income and Corporation Taxes Act 1988.
(5)For the purposes of this section the year of assessment which corresponds to a tax year is the year of assessment (within the meaning of the Tax Acts) which consists of the same period as that tax year.