1(1)For the purposes of determining whether Class 1 contributions are payable in respect of earnings paid to an earner in a given week and, if so, the amount of the contributions—
(a)all earnings paid to him or for his benefit in that week in respect of one or more employed earner’s employments under the same employer shall, except as may be provided by regulations, be aggregated and treated as a single payment of earnings in respect of one such employment; and
(b)earnings paid to him or for his benefit in that week by different persons in respect of different employed earner’s employments shall in prescribed circumstances be aggregated and treated as a single payment of earnings in respect of one such employment;
and regulations may provide that the provisions of this sub-paragraph shall have effect in cases prescribed by the regulations as if for any reference to a week there were substituted a reference to a period prescribed by the regulations.
(2)Where earnings in respect of employments which include any contracted-out employment and any employment which is not a contracted-out employment are aggregated under sub-paragraph (1) above and the aggregated earnings are not less than the current lower earnings limit, then, except as may be provided by regulations—
(a)the amount of the primary Class 1 contribution in respect of the aggregated earnings shall be determined in accordance with sub-paragraph (3) below; and
(b)the amount of the secondary Class 1 contribution in respect of the aggregated earnings shall be determined in accordance with sub-paragraph (6) below.
(3)The amount of the primary Class 1 contribution shall be the aggregate of the amounts obtained—
(a)by applying the rates of primary Class 1 contributions that would apply if the aggregated earnings were all attributable to contracted-out employments—
(i)to the part of the aggregated earnings attributable to any such employments, or
(ii)if that part exceeds the current upper earnings limit, to so much of that part as does not exceed that limit; and
(b)if that part is less than that limit, by applying the rate of primary Class 1 contributions that would apply if the aggregated earnings were all attributable to employments which are not contracted-out to so much of the remainder of the aggregated earnings as, when added to that part, does not exceed that limit.
(4)In relation to earners paid otherwise than weekly, any reference in sub-paragraph (2) or (3) above to the lower or upper earnings limit shall be construed as a reference to the prescribed equivalent of that limit.
(5)The power under sub-paragraph (4) above to prescribe an equivalent of a limit includes power to prescribe an amount which exceeds, by not more than £1.00, the amount which is the arithmetical equivalent of that limit.
(6)The amount of the secondary Class 1 contribution shall be the aggregate of the amounts obtained—
(a)by applying the rates of secondary Class 1 contributions that would apply if the aggregated earnings were all attributable to contracted-out employments to the part of the aggregated earnings attributable to any such employments; and
(b)by applying the rate of secondary Class 1 contributions that would apply if the aggregated earnings were all attributable to employments which are not contracted-out to the remainder of the aggregated earnings.
(7)Where any single payment of earnings is made in respect of two or more employed earner’s employments under different employers, liability for Class 1 contributions shall be determined by apportioning the payment to such one or more of the employers as may be prescribed, and treating a part apportioned to any employer as a separate payment of earnings by him.
(8)Where earnings are aggregated under sub-paragraph (1)(b) above, liability (if any) for the secondary contribution shall be apportioned, in such manner as may be prescribed, between the secondary contributors concerned.