S.D. Codified Laws § 3-12C-403
All employee and employer contributions to the system and the necessary supporting data shall be transmitted by the employer at least monthly to the system. Each monthly transmission for each respective calendar month shall be completed by the fifteenth day of the following month. All supporting data shall be transmitted electronically in a format determined by system personnel. All contributions shall be deposited with the state treasurer in the fund established to administer this chapter. If any participating unit fails to deliver contributions with respect to compensation paid in any month and the necessary supporting data by the fifteenth day of the following month, the participating unit shall pay to the system a penalty equal to five percent of the delinquent contributions. The delinquent contributions and the penalty shall bear interest at the assumed rate of return from the date due until the date paid. In calculating accumulated contributions, all contributions with respect to compensation paid in any fiscal year shall be included in the calculation of interest credited for that fiscal year.
SDCL 3-12C-403