S.D. Codified Laws § 3-12C-810
For the first thirty-six months of a disability benefit provided by § 3-12C-805, the maximum amount a member may receive in any calendar year from the disability benefit and earned income, as defined in § 32(c)(2) of the Internal Revenue Code, is one hundred percent of the member's final average compensation. Starting with the thirty-seventh month of the disability benefit, the maximum amount that a member may receive in any calendar year from disability benefits provided by the federal Social Security Act equal to the primary insurance amount, the disability benefit provided by this chapter and earned income, as defined in § 32(c)(2) of the Internal Revenue Code, is one hundred percent of the member's final average compensation. The maximum amount shall be indexed for each full fiscal year during which the member is eligible for such disability benefit by the COLA. Any amount exceeding this maximum amount shall reduce each monthly disability benefit payable pursuant to § 3-12C-805 in the following fiscal year on a pro rata basis.
Any member eligible to receive a disability benefit shall report to the system in writing any earned income of the member. The report shall be filed with the system before June first following the end of each calendar year in which a disability benefit is paid. A disabled member may file a signed copy of the member's individual income tax return in lieu of the report. No report or return need be filed for the calendar year the member dies or converts to a normal or early retirement benefit under this chapter. The disability benefit of any member failing to file a report or return as required in this section shall be suspended until the report or return is filed. The reduction may occur, however, only if a disability benefit is being paid by the system, but may not reduce the disability benefit below the minimum provided for in § 3-12C-805.
This section applies to any member receiving or entitled to receive a disability benefit pursuant to § 3-12C-803.
SDCL 3-12C-810