19-20-410. Creditable service for extension service employment. (1) (a) Subject to 19-20-405, at any time before retirement, a vested member may file a written application with the retirement board to purchase up to 5 years of employment service with the Montana cooperative extension service if:

(i) the member became a member of the retirement system before July 1, 1989;

(ii) the service involved instructional service at a unit of the Montana university system; and

(iii) the member received a refund of membership contributions under the civil service retirement system or the federal employees' retirement system for the service to be purchased.

(b) For each year of service to be purchased under subsection (1)(a), the member shall contribute to the retirement system an amount equal to the combined employer and employee contribution rate in effect at the time that the member is eligible to purchase the service multiplied by the member's first full year's salary earned in a position reportable to the retirement system subsequent to the member's extension service employment, plus interest paid as follows:

(i) if a written application to purchase service was signed prior to July 1, 2012, at the rate that the contribution would have earned had the contribution been in the member's account upon the member becoming vested; or

(ii) if a written application to purchase service is signed on or after July 1, 2012, at the actuarially assumed interest rate in effect on the date the written application is signed.

(2) In addition to service purchased under subsection (1) and subject to 19-20-407, a member who has purchased 5 years or more of creditable service in the retirement system may purchase additional years of cooperative extension service by contributing to the system the full actuarial cost of the service.

(3) Contributions to purchase service under this section may be made in a lump-sum payment or in installments as agreed upon by the member and the retirement board.