S.D. Codified Laws § 54-3-16 : — DEBTOR AND CREDITORINTEREST AND USURY —3-16 - Official state interest rates TEXT PDF The official state interest rates, as referenced throughout the South Dakota Codified Laws, are as follows: (1) Category A rate of interest is four and one-half percent per year; (2) Category B rate of interest is ten percent per year; (3) Category C rate of interest is twelve percent per year; (4) Category D rate of interest is one percent per month or fraction thereof; (5) Category E rate of interest is four percent per year; (6) Category F rate of interest is fifteen percent per year; and (7) Category G rate of interest is five-sixth percent per month or fraction thereof. SDCL 54-3-16 SL 1984, ch 319, § 1; SL 1987, ch 362; SL 1994, ch 366, § 1; SL 2000, ch 226, §1.