24. For the purpose of determining the amount of earnings-related contributions, the amount of a person’s earnings from employed earner’s employment shall be calculated on the basis of his gross earnings from the employment or employments in question.
This is subject to the provisions of Schedule 2 (calculation of earnings for the purposes of earnings-related contributions in particular cases) and Schedule 3 (payments to be disregarded in the calculation of earnings for the purposes of earnings-related contributions).