S.D. Codified Laws § 21-49-35
A written notice of redemption shall be served on the purchaser and the person making the sale by the person seeking to redeem. If such person redeem as holder of a judgment, notice shall be a certified copy thereof. If such person redeem as holder of a mortgage or other lien, notice shall be a certified copy of the record thereof, together with a certified copy of any assignment to establish his claim, and an affidavit showing the amount then actually due on the lien; and at the same time shall pay to the person making the sale the amount prescribed by § 21-49-34. If such person redeem as a successor in interest of a judgment debtor, notice shall be proof of interest in such property.
A duplicate of the notice of redemption with proof of service shall be forthwith filed for record with the register of deeds of the counties where the property is located.
SDCL 21-49-35