Mo. Rev. Stat. § 137.081: New political subdivisions, assessment, effective when.

For purposes of assessment under this chapter, any new political subdivision that is created by approval of the voters before July first of any assessment year shall be considered effective for assessment purposes upon certification of such vote. If the new political subdivision is created by approval of the voters on or after July first of the current assessment year, the new political subdivision shall be considered effective for assessment purposes in the following assessment year.