The amount of a contribution in respect of State pension (contributory) to be returned to an insured person under article 75 shall be -

(a) where the contribution was due on or after the 6th day of April, 1982 -

(i) in the case of an employment contribution paid at the rate specified in 10(1)(b), 1.06%, or

(ii) in the case of a voluntary contribution paid at the rate specified in section 22(1)(b)(ii) or (iii), 2.74%,

of the amount of the reckonable earnings or the reckonable income, as appropriate, by reference to which the contribution paid was determined, and

(b) where the contribution was due before the 6th day of April, 1982, at the appropriate rate specified in Schedule B.