Missouri Revised Statutes Title XXVI. Trade and Commerce § 408.150. Lender can not receive excess interest--failure by lender to return excess interest, damages allowed

If any amount in excess of the interest permitted by sections 408.100 to 408.190 is charged or received on any loan except as the result of a bona fide error, the lender shall be barred from recovery of any interest on the contract and shall upon demand return all interest received to the person from  1 whom received. If such interest is not returned upon written demand, then the person paying the same or his legal representative may recover twice the amount paid together with costs of the suit and reasonable attorney's fees, provided that the action is brought within five years of such written demand.