Mo. Const. art. X, § 3

Taxes may be levied and collected for public purposes only, and shall be uniform upon the same class or subclass of subjects within the territorial limits of the authority levying the tax. All taxes shall be levied and collected by general laws and shall be payable during the fiscal or calendar year in which the property is assessed. Except as otherwise provided in this constitution, the methods of determining the value of property for taxation shall be fixed by law. [Effective - 02 Sep 1982 , see footnote]