Mo. Rev. Stat. § 234.290
In the issuance of toll bridge revenue bonds or toll bridge revenue refunding bonds under the provisions of sections 234.210 to 234.300, the issuing authority may reserve unto itself the right, at its option, to call in, pay and redeem such bonds prior to the maturity date or dates thereof at such premium as such issuing authority may designate in such bonds, but not exceeding a premium equal to five percent of the principal amount of such bonds; provided, however, that whenever it is desired to exercise the aforesaid right, if reserved in such bonds, the issuing authority shall cause written notice thereof to be delivered to the bank or office at which such bonds are payable, and such notice shall be so delivered not less than thirty days prior to the interest payment date designated for the redemption of such bonds, after which date, so designated, no further interest shall accrue on the bonds so called for redemption. Notice of the exercise of such right shall also be filed with the state auditor of Missouri, as provided by section 108.260.
§ 234.290, RSMo