S.D. Codified Laws § 13-55E-3
Notwithstanding § 13-55E-2, benefits provided under contract may commence within a period less than seventeen years but not less than ten years from the beginning date of the first fall academic semester following the date of payment. The one-time advance payment required under a contract providing for a reduced time limitation on the use of contract benefits pursuant to this section shall be subject to interest compounded annually at the rate of ten percent for the period of time the contract is reduced below seventeen years, payable at the time of advance payment. The amount of the one-time advance payment together with interest paid under this section shall be refunded upon termination or modification of the contract pursuant to § 13-55E-10. Any investment earnings accruing to a contract under this section are not refundable.
SDCL 13-55E-3