169.570.  Employment of person having rights in more than one retirement system, may purchase membership credit — purchase of equivalent credit, when, requirements. — 1.  An employee having less than five years of membership service under one of the Missouri retirement systems provided in sections 169.010 to 169.141, 169.270 to 169.400 or 169.410 to 169.540, who is subsequently employed in a position covered by another of the Missouri retirement systems, may elect within five years after employment in a district included in another of the Missouri retirement systems to purchase membership credit for service rendered under the first system; provided, however, that the employee shall be entitled to apply the membership credit thus purchased toward a service retirement only and not for any other benefit.  The purchase shall be effected by the member paying to the retirement system the amount required by the rules and regulations established by the respective retirement system, or, absent such rules and regulations, an amount, with interest, based on the annual salary rate of the employee's initial employment in a district under the system in which credit is being purchased and the contribution rate in effect in that system at the date of election to purchase credit.  In the retirement systems provided by sections 169.270 to 169.400 and 169.410 to 169.540, the school district shall contribute the amount required by the statutes and by the rules and regulations established by the system for each year of creditable service purchased by the incoming member.

  2.  A member of any Missouri public school retirement system established by sections 169.010 to 169.141, 169.270 to 169.400, 169.410 to 169.540, or 169.600 to 169.715 who has previous credit in one of the other Missouri public school retirement systems may elect to purchase equivalent credit in the member's present system provided such credit toward retirement is withdrawn and benefits terminated in the previous system.  The purchase shall be effected by the member paying to the retirement system the amount required by the rules and regulations established by the respective retirement system, or absent such rules and regulations, an amount, with interest, based on the annual salary rate of the member's initial employment in a district under the system in which credit is being purchased and the contribution rate in effect in that system at the date of election to purchase credit.

  3.  Nothing in this section shall decrease or discontinue the benefits provided by the sections of the statutes relating to any of the public school retirement systems in the state of Missouri.

  4.  Payment pursuant to the provisions of this section shall be completed prior to termination of membership with the retirement system, with interest on the unpaid balance, in accordance with rules and regulations and statutes established by the respective retirement systems.  The individual purchasing credit must have service credit as a member of the retirement system for at least as many years before retirement as the number of years of credit being purchased.