“ 13 Class 3 contributions (1) The Treasury shall by regulations provide for earners and others, if over the age of 16, to be entitled if they so wish, but subject to any prescribed conditions, to pay Class 3 contributions; … 13A Right to pay additional Class 3 contributions in certain cases (1) An eligible person is entitled, if he so wishes, but subject to any conditions prescribed by regulations made by the Treasury and to the following provisions of this section, to pay Class 3 contributions in respect of a missing year. (2) A missing year is a tax year not earlier than 1975–76 in respect of which the person would under regulations under section 13 be entitled to pay Class 3 contributions but for a limit on the time within which contributions may be paid in respect of that year. (3) A person is not entitled to pay contributions in respect of more than 6 tax years under this section. (4) A person is not entitled to pay any contribution under this section after the end of 6 years beginning with the day on which he attains pensionable age. (5) A person is an eligible person if the following conditions are satisfied. (6) The first condition is that the person attained or will attain pensionable age in the period— (a) beginning with6th April 2008 , and (b) ending with5th April 2015 . (7) The second condition is that there are at least 20 tax years each of which is a year to which subsection (8) or (10) applies … (10) This subsection applies (in the case of a person who attained or will attain pensionable age before6th April 2010 ) if the year is one in which the person was precluded from regular employment by responsibilities at home within the meaning of regulations under paragraph 5(7) of Schedule 3. (11) The third condition applies only if the person attained or will attain pensionable age before6th April 2010 . (12) That condition is that— (a) the person has, in respect of any one tax year before that in which he attains pensionable age, actually paid contributions that are of a relevant class for the purposes of paragraph 5 of Schedule 3, and (b) in the case of that year, the earnings factor derived as mentioned in subsection (13) is not less than the qualifying earnings factor for that year. (13) For the purposes of subsection (12)(b) the earnings factor— (a) in the case of 1987–88 or any subsequent year, is that which is derived from— (i) so much of the person’s earnings as did not exceed the upper earnings limit and upon which such of the contributions mentioned in subsection (12)(a) as are primary Class 1 contributions were paid or treated as paid, and (ii) any Class 2 or Class 3 contributions for the year, or (b) in the case of any earlier year, is that which is derived from the contributions mentioned in subsection (12)(a). 14 Restriction on right to pay Class 3 contributions (1) No person shall be entitled to pay a Class 3 contribution in respect of any tax year if his earnings factor, or the aggregate of his earnings factors, for that year derived— (a) in the case of 1987–88 or any subsequent year, from earnings upon which Class 1 contributions have been paid or treated as paid or from Class 2 contributions actually paid; or (b) in the case of any earlier year, from contributions actually paid, is equal to or exceeds the qualifying earnings factor for that year; and regulations may provide for precluding the payment of Class 3 contributions in other cases .…”
“A woman who has made, or is under the regulations 126 to 131 treated as having made, an election under regulation 127 shall be precluded from paying Class 3 contributions for any year in respect of the whole of which that election has effect.”
“This Directive shall be without prejudice to the right of Member States to exclude from its scope: … (e) the consequences of the exercise, before the adoption of this Directive, of a right of option not to acquire rights or incur obligations under a statutory scheme.”