(1) The Principal Act is hereby amended by the substitution for section 17C (inserted by section 11 of the Act of 1988) of the following section:
"17C. Rates of self-employment contributions and related matters.
Self-employment contributions shall be paid by self-employed contributors in accordance with the following provisions:
(a) Subject to paragraphs (b), (d) and (i), where in any contribution year a self-employed contributor has reckonable income there shall be payable by him a self-employment contribution which shall be of an amount equal to 5 per cent. of the reckonable income or the amount of £234, whichever is the greater.
(b) Where for any contribution year a self-employed contributor is informed by the Revenue Commissioners that he is not required to make a return of income within the meaning of section 48(1) of the Finance Act, 1986, self-employment contributions shall be paid by the self-employed contributor (whether by instalments or otherwise as may be prescribed)