1. Members who have accrued at least one year of membership service credit for employment in a position covered by this retirement system and who have covered employment with this retirement system following the service for which credit is being purchased may purchase membership service credit under the circumstances, terms and conditions provided in this section. With respect to each such purchase authorized by this section the following provisions apply:
(1) The purchase shall be effected by the member paying to the retirement system the amount the member would have contributed and the amount the employer would have contributed had such member been an employee for the number of years for which the member is electing to purchase credit, and had the member's compensation during such period been the highest annual salary rate on record with the retirement system on the date of election to purchase credit. The contribution rate used in determining the amount to be paid shall be the contribution rate in effect on the date of election to purchase credit. Notwithstanding the provisions of this subsection, for all elections to purchase credit received by the retirement system on or after January 1, 2006, the member shall receive credit based on the amount paid by the member for such credit and received by the retirement system by the close of business on June thirtieth of each year. In lieu of charging the member interest on such purchase of credit, the amount to be paid by the member for any remaining credit the member has elected to purchase but has not paid for by September thirtieth of each year shall be recalculated on the following October first using the contribution rate in effect on that July first and the highest salary of record for the member as of that July first. For all elections to purchase credit received by the retirement system prior to January 1, 2006, the retirement system shall determine the cost of such purchase using the calculation method in effect for elections to purchase credit received by the retirement system on or after January 1, 2006, provided that the member shall have a one-time, irrevocable option to continue to have the cost of such purchase be determined using the calculation method in effect at the time of such election to purchase such credit. To be effective, such option must be elected by the member on a form approved by the retirement system and such form must be received by the retirement system by the close of business on June 30, 2006. The retirement system reserves the right to prohibit a purchase, impose additional requirements for making a purchase, or limit the amount of credit purchased if necessary for the retirement system to comply with federal law, including but not limited to, the provisions of Section 415 of Title 26 of the United States Code. The board of trustees may promulgate such rules and regulations consistent with the provisions of this section deemed necessary for its proper administration, pursuant to the provisions of this section and this chapter. Any rule or portion of a rule, as that term is defined in section 536.010 , that is created under the authority delegated in this section shall become effective only if it complies with and is subject to all of the provisions of chapter 536 and, if applicable, section 536.028 . This section and chapter 536 are nonseverable and if any of the powers vested with the general assembly pursuant to chapter 536 to review, to delay the effective date, or to disapprove and annul a rule are subsequently held unconstitutional, then the grant of rulemaking authority and any rule proposed or adopted after August 28, 2009, shall be invalid and void;
(2) Membership service credit purchased pursuant to this section shall be deemed to be membership service as defined in subdivision (10) of section 169.600 ;
(3) An election to purchase membership service credit pursuant to this section and payment for the purchase shall be completed prior to termination of membership with the retirement system with interest on the unpaid balance;
(4) Members may purchase membership service credit in increments of one-tenth of a year, and multiple elections to purchase may be made;
(5) Additional terms and conditions applicable to purchases made pursuant to this section including, but not limited to, minimum payments, payment schedules and provisions applicable when a member fails to complete payment may be set by rules of the board.
2. Membership service credit shall not be allowed pursuant to this section or sections 169.570 and 169.577 which exceeds in length the member's membership service credit for employment in a position covered by this system, and in no event may the member receive membership service credit with both this system and another public retirement system for the same service.
3. A member who was employed for at least twenty hours per week on a regular basis by a public school district, public community college, public college, or public university, either inside or outside of this state, may elect to purchase equivalent membership service credit.
4. A member who has served in the Armed Forces of the United States of America and who was discharged or separated from the Armed Forces by other than a dishonorable discharge may elect to purchase membership service credit for the period of active duty service in the Armed Forces.
5. Any member granted unpaid maternity or paternity leave for a period, from a position covered by the retirement system, who returned to employment in such a position, may elect to purchase membership service credit for the period of leave.
6. Any member who is or was certified as a vocational-technical teacher on the basis of having a college degree or who was required to have a period of work experience of at least two years in the area of the subject being taught in order to qualify for such certification may, upon written application to the board, purchase equivalent membership service credit for such work experience which shall not exceed the two years necessary for certification if the work experience was in the area that the member taught or is teaching and was completed in two years.
7. Any member who had membership service credit with the public school retirement system of Missouri governed by sections 169.010 to 169.141 but which membership service credit was forfeited by withdrawal or refund may elect to purchase credit for such service. The public school retirement system of Missouri shall transfer to this system an amount equal to the employer contributions for the forfeited service being purchased, plus interest, which shall be applied to reduce the amount the member would otherwise pay for the purchase, provided that the amount transferred shall not exceed one-half of the purchase cost.
8. A member may elect to purchase membership service credit for service rendered while on leave from an employer, as defined in section 169.600 , for a not-for-profit corporation or agency whose primary purpose is support of education or education research if the member was employed by that organization to serve twenty or more hours per week on a regular basis.
9. A member who was employed by a private school, private community college, private college, or private university, either inside or outside of this state, for at least twenty or more hours per week on a regular basis, may elect to purchase membership service credit for such service rendered.
10. A member who was employed in nonfederal public employment for at least twenty hours a week on a regular basis shall be permitted to purchase equivalent creditable service in the retirement system for such employment subject to provisions of this section.
11. A member who, while eighteen years of age or older, was employed in a position covered by Social Security for at least twenty hours a week on a regular basis shall be permitted to purchase equivalent creditable service in the retirement system for such employment subject to provisions of this section.