Mo. Rev. Stat. § 32.069 – Interest allowed and paid on refund or overpayment of interest paid in excess of annual interest rate

Notwithstanding any other provision of law to the contrary, interest shall be allowed and paid on any refund or overpayment at the rate determined by section 32.068 only if the overpayment is not refunded within one hundred twenty days, or within ninety days in the case of taxes imposed by sections 143.011 and 143.041, from the latest of the following dates:

(1) The last day prescribed for filing a tax return or refund claim, without regard to any extension of time granted;
(2) The date the return, payment, or claim is filed; or
(3) The date the taxpayer files for a credit or refund and provides accurate and complete documentation to support such claim.

(L. 2002 S.B. 1248, A.L. 2007 S.B. 613 Revision, A.L. 2010 H.B. 1408 & 1514)