Where a secondary Class 1 contribution is payable as mentioned in section 6(1)(b) above, the amount of that contribution shall be F2the relevant percentage of so much of the earnings paid in the tax week, in respect of the employment in question, as exceeds the current secondary threshold (or the prescribed equivalent).

For the purposes of this Act the secondary percentage is F615%; but that percentage is subject to alteration under sections 143 and 145 of the Administration Act.