Mo. Rev. Stat. § 139.055

Any county or public water supply district may accept payment by credit card or electronic transfers of funds for any tax, fee, or license payable to the county or district. A county collector or district shall not be required to accept payment by credit card if the credit card bank, processor, or issuer would charge the county or district a fee for such payment. However, a county or district may accept payment by credit card and charge the person making such payment by credit card a fee equal to the fee charged the county or district by the credit card bank, processor, issuer for such payment. A county or district may accept payment by electronic transfer of funds in payment of any tax, fee, or license and charge the person making such payment a fee equal to the fee charged the county or district by the bank, processor, or issuer of such electronic payment.