Mo. Rev. Stat. § 139.040
A county or city collector, or other collection authority charged with the duty of tax or license collection is authorized but not obligated to accept cash, personal check, business check, money order, credit card, or electronic transfers of funds for any tax or license payable to the county. The collection authority may refuse to accept any medium of exchange at the discretion of the collection authority including any medium of exchange submitted without the statement of property taxes due and assessed as required by section 52.230. Refusal by the collection authority to accept alternative means of payment beyond those approved by the collection authority shall not relieve an obligor of the obligor's tax or license obligation nor shall it delay the levy of interest and penalty on any overdue unpaid tax or license obligation pending submission of a form or payment approved by the collection authority.
§ 139.040, RSMo
RSMo 1939 § 11082, A.L. 1945 p. 1820, A.L. 1959 H.B. 106, A.L. 2005 H.B. 58 merged with S.B. 210, A.L. 2010 H.B. 1316