S.D. Codified Laws § 3-12C-1001
Within three hundred sixty-five days of becoming a member, within ninety days of attaining age thirty-five, or within ninety days of the first anniversary of a marriage, a member may elect to provide the member's spouse with additional survivor protection by increasing the member's contribution by an additional one and five-tenths percent of compensation, which additional contribution may not be matched by the member's employer. The additional contribution shall commence with the first payroll period following the date of the election. It shall continue until the earlier of the member's spouse attaining age sixty-five, the death or disability of the member, the death of the spouse, termination of employment or the termination of the marriage as defined in the rules of the board of trustees. The additional contribution may not be treated as a member contribution for purposes of determining the amount of refund of accumulated contributions. However, the contributions paid prior to January 1, 1979, shall be considered part of accumulated contributions for determining the amount of refund if the member terminates employment. Notwithstanding any other provision of this section, a member who is currently contributing to the system may terminate the additional survivor protection under this section, but all funds contributed for the additional survivor protection shall remain with the system and may not be considered as part of the member's accumulated contributions. For the purposes of implementing this section, the one and two-tenths percent contribution for additional survivor protection was applied to all compensation received on or after July 1, 2004, regardless of when that compensation was earned, and the one and five-tenths percent of compensation shall be applied to all compensation received on or after July 1, 2010, regardless of when that compensation was earned.
SDCL 3-12C-1001