Mo. Rev. Stat. § 140.750: Commission allowed on collection of revenue.

All officers required by law to receive and pay over to the collectors any part of the state and county revenue shall receive as full compensation, commission on the amount received at the rate of two percent; provided, that in counties of the first and second class and the city of St. Louis, such commission shall be paid by all officers receiving such compensation to the county or city treasury as provided by law.