Mo. Rev. Stat. § 31.050
Whenever any person has been received as a patient of any institution or hospital of the department of mental health, and thereafter the county, municipality, guardian, trustee or person responsible for the support of the patient neglects or refuses to pay, within the time and in the manner required by law or the rules and regulations of the department of revenue, any installment required to be paid for the support of the patient, the superintendent of the institution or hospital may return the patient to the sheriff of the county or municipality or to the guardian, trustee or person responsible for the payment of the installment, and at the expense of the county, municipality, guardian, trustee or person. No such patient shall be so returned until the department of mental health has notified the county or municipality or guardian, trustee or person responsible for the support of such patient in writing that there exists a shortage in payment of such support and that unless the same is paid within thirty days such patient will be so returned.
§ 31.050, RSMo