Mo. Const. art. VI, § 28

For the purpose of refunding, extending, and unifying the whole or any part of its valid bonded indebtedness any county, city, school district, or other political corporation or subdivision of the state, under terms and conditions prescribed by law may issue refunding bonds not exceeding in amount the principal of the outstanding indebtedness to be refunded and the accrued interest to the date of such refunding bonds. The governing authority shall provide for the payment of interest at not to exceed the same rate, and the principal of such refunding bonds, in the same manner as was provided for the payment of interest and principal of the bonds refunded. [Effective - 27 Feb 1945 , see footnote]