Subdivision (1) of section 4 of chapter 32 of the General Laws, as appearing in the 2014 Official Edition, is hereby amended by striking out paragraph (b) and inserting in place thereof the following paragraph:-

(b) Periods of service in any governmental unit prior to the date a system becomes operative therein rendered by any employee who becomes a member when such system first becomes operative in such governmental unit, or who becomes a member as otherwise provided for in paragraph (f) of subdivision (6) of section 3, shall, subject to the provisions and limitations of sections 1 to 28, inclusive, be counted as creditable prior service; provided, however, that after becoming a member and before the date any retirement allowance becomes effective, the person pays into the annuity savings fund of the system in 1 sum, or in installments, upon such terms and conditions as the board may prescribe, payments of an amount equal to that which would have been withheld as regular deductions from the person’s  regular compensation had the person been eligible for membership and been a member of such system during such previous period, together with buyback interest; provided further, that in no event shall any such person be credited with more than 1 year of creditable service for all such prior service rendered during any 1 calendar year.