S.D. Codified Laws § 32-9-21
Each motor carrier desiring to discontinue using a vehicle as a commercial motor vehicle, may, on or before the termination of any year as provided in § 32-9-17, return the commercial motor vehicle plates and certificates to the county treasurer of the county where the vehicle was registered together with an application for the discontinuance. Upon satisfactory evidence that the carrier will not further operate the vehicle as a commercial motor vehicle, the county treasurer shall issue to the person, corporation, or limited liability company, so applying, a warrant for the amount due for the remaining months of that year less a ten dollar administrative fee which shall be retained by the county. The commercial motor vehicle plates and certificates shall be in the possession of the county treasurer on or before the fifth day of the month to receive credit for that month.
SDCL 32-9-21