19(1) Regulations may provide either generally or in relation to–
(a)any prescribed category of earners; or
(b)earners in any prescribed category of employments,
that their liability in a particular tax year in respect of contributions of prescribed classes, or any prescribed part of such contributions, is not to exceed such maximum amount or amounts as may be prescribed.
19(2) Regulations made for the purposes of subsection (1) above may provide–