Mo. Rev. Stat. § 251.400
For the purpose of providing funds to meet the expenses of a regional planning commission, the commission shall annually prepare and approve a budget reflecting the costs of its operations and services to the local governmental units within the region. The amount charged to each local unit shall be in the proportion that its assessed valuation bears to the total, or such other method as may be agreed upon by the governmental units within the region. The budget as prepared by the regional planning commission shall show the proportionate share of each local governmental unit participating in such commission and shall be submitted to each participating local governmental unit at least sixty days prior to the end of the regional planning commission's fiscal year. The budget as submitted shall be approved by local governmental units which represent more than fifty percent of the assessed valuation of the participating local units.
§ 251.400, RSMo