Mo. Rev. Stat. § 288.140
If not later than three years after the date on which any contributions would have been required to be paid if due, an employing unit who has paid such contributions or interest thereon shall make application for an adjustment thereof in connection with subsequent contribution payments, or for a refund thereof because such adjustment is not practicable, and if the division shall determine that such contributions or interest or any portion thereof was erroneously collected, the division shall make an adjustment thereof, without interest, in connection with subsequent contribution payments, or if such adjustment is not practicable, the division shall refund such payment, without interest, from the fund. The division may, in its discretion, at any time and under such conditions and limitations as it may deem proper, make an adjustment or refund of contributions or interest paid thereon which the division finds has been erroneously collected, or any part thereof, if it finds there is good cause why such adjustment or refund should be made. The division shall not be required to refund any contributions based upon wages payable or paid which have been included in a determination of a claimant's benefit rights and which determination has become final.
§ 288.140, RSMo