13. A person who is contributing in accordance with the Act respecting the Government and Public Employees Retirement Plan (chapter R-10), a person who has complied with section 6 and, subject to the exception set forth in section 12, a person referred to in paragraph 2 of section 2, must redeem, in accordance with section 12, a number of years and parts of a year of service which cannot be greater than the excess of the number of years and parts of a year prior to 1 July 1973 credited under section 10 or 11, as the case may be, or standing to their credit pursuant to paragraph 2 of section 2, over 15.
Where a person contributed to a supplemental pension plan while employed by an employer contemplated in the Act respecting the Government and Public Employees Retirement Plan, the years and parts of a year prior to 1 July 1973 in respect of which he was granted a pension credit under section 101 of the said Act or in respect of which a paid-up annuity certificate was issued must be included in computing the excess over 15 referred to in the first paragraph.