S.D. Codified Laws § 43-41B-36
All agreements to pay compensation to recover or assist in the recovery of property reported under § 43-41B-18, made within twelve months prior to the reporting and remitting of abandoned property accounts and within twenty-four months after the date payment or delivery is made under § 43-41B-20, are unenforceable. No agreement entered into after twenty-four months of the required date of delivery of the property by the holder to the state treasurer is valid if a person thereby undertakes to locate property included in a report for a fee or other compensation exceeding twenty-five percent of the value of the recoverable property unless the agreement is in writing and signed by the owner. Nothing in this section may be construed to prevent an owner from asserting at any time that an agreement to locate property is based upon excessive or unjust consideration. A violation of this section is a Class 1 misdemeanor.
SDCL 43-41B-36