(1) Subject to subsections (3), (3A) and (4) of this section and to section 79, where a person ceases to be an eligible employee by reason of retirement on the ground of invalidity before attaining his or her maximum retiring age then, except in a case where subsection (2) of this section applies, the person is entitled:
(a) if the person does not make an election under section 68 or 69--to invalidity pension in accordance with section 67 and, where the person has paid supplementary contributions, a lump sum benefit in accordance with that section;
(b) if the person makes an election under section 68--to invalidity pension, and a lump sum benefit, in accordance with that section; or
(c) if the person is entitled to make an election under section 69 and makes such an election--to a lump sum benefit in accordance with that section.
(2) Subject to subsections (3), (3A) and (4) of this section and section 79, where:
(a) a person ceases to be an eligible employee by reason of retirement on the ground of invalidity before attaining his or her maximum retiring age;
(b) there was in force in respect of the person, immediately before the person's retirement, a benefit classification certificate; and
(c) CSC is of the opinion that the incapacity which was the ground for his or her retirement was caused, or was substantially contributed to, by a physical or mental condition or conditions specified in the certificate or by a physical or mental condition or conditions connected with such a condition or such conditions;
the person is entitled:
(d) where the period of contributory service of the person is not less than 8 years:
(i) if the person does not make an election under section 71 or 72--to invalidity pension in accordance with section 70 and, where the person has paid supplementary contributions, a lump sum benefit in accordance with that section;
(ii) if the person makes an election under section 71--to invalidity pension, and a lump sum benefit, in accordance with that section; or
(iii) if the person is entitled to make an election under section 72 and makes such an election--to a lump sum benefit in accordance with that section; or
(e) where the period of contributory service of the person is less than 8 years--to a lump sum benefit in accordance with section 73.
(2A) Where CSC is of the opinion that:
(a) a person will, in the near future, cease to be an eligible employee by reason of retirement on the ground of invalidity before attaining the person's maximum retiring age;
(b) there will be in force in respect of the person, immediately before the person's retirement, a benefit classification certificate; and
(c) the incapacity which will be the ground for the person's retirement was caused, or was substantially contributed to, by a physical or mental condition or conditions specified in the certificate or by a physical or mental condition or conditions connected with such a condition or such conditions;
then:
(d) CSC shall inform the person in writing that CSC had formed the opinions referred to in paragraphs (a), (b) and (c); and
(e) where the person becomes a person referred to in paragraph (2)(a) and to whom paragraph (2)(b) applies, CSC shall be taken to have formed the opinion referred to in paragraph (2)(c) in relation to that person immediately on the person becoming a person referred to in paragraph (2)(a) unless, whether before or after the person became a person so referred to, CSC informed the person in writing that this subsection is not to apply to the person.
(2B) Where CSC forms the opinion referred to in paragraph (2)(c) in relation to a person on a date after the date on which the person retired, any payment to that person before the first - mentioned date of benefit or of pension purported to be made under subsection (2) shall be deemed to have been as valid as it would have been if CSC had formed that opinion immediately on the person's retirement.
(3) Where a person to whom invalidity pension had been payable in accordance with section 68 or 71 again became an eligible employee and later ceases to be an eligible employee by reason of retirement on the ground of invalidity before attaining his or her maximum retiring age, he or she is not entitled to invalidity benefit in accordance with section 67 or 70, but he or she is entitled to invalidity benefit in accordance with section 68 or 71, as the case may be, as if he or she had made an election under whichever of those sections is applicable.
(3A) Where:
(a) a person ceases to be an eligible employee and, upon his or her so ceasing, deferred benefits become applicable in relation to him or her by virtue of Division 3 of Part IX;
(b) deferred benefits cease to be applicable in relation to the person upon a deferred benefit by way of invalidity pension becoming payable to him or her in accordance with section 68 or 71;
(c) the deferred benefit is cancelled under subsection 76(1) upon his or her again becoming an eligible employee or is cancelled under subsection 143(2); and
(d) the person later ceases to be an eligible employee by reason of retirement on the ground of invalidity before attaining his or her maximum retiring age or becomes entitled to deferred benefit by way of invalidity benefit;
the person is not entitled to invalidity benefit in accordance with section 67 or 70, but he or she is entitled to invalidity benefit in accordance with section 68 or 71, as the case may be, as if he or she had made an election under whichever of those sections is applicable.
(3B) Subsections (3) and (3A) shall not be taken to prevent a person who would, but for those subsections, be entitled to make an election under section 69 or 72 from making such an election and becoming entitled to invalidity benefit in accordance with whichever of those sections is applicable.
(4) Subsections (1) and (2) do not apply to a person whose period of prospective service is less than 1 year.