Mo. Rev. Stat. § 92.170: Employers may collect tax, and allowance may be authorized.

Any such city is hereby authorized to impose upon employers the duty of collecting and remitting to the city any tax that may be levied upon the earnings of employees pursuant to sections 92.110 to 92.200, and to prescribe penalties for failure to perform such duty. In the event that any such city should impose such duty on employers, each such employer shall be entitled to deduct and retain one and one-half percent of the total amount collected to compensate such employer for collecting such tax. The governing body of any such city may, by ordinance, reduce, eliminate, or reimpose, if eliminated, the fee allowed to employers by this section.