Mo. Rev. Stat. § 50.055

The accounts of any county of the second class, or the accounts of any officer or office of such county, may be audited at any time, if the county commission determines such an audit desirable or necessary, either by a certified public accountant employed by the county commission or by the state auditor, as the county commission may determine. If the audit is to be made by the state auditor, the state auditor shall be requested by the county commission to make the audit, as provided by law. Unless the audit is requested for a particular officer or office, the audit may also review the records of the receipts and disbursements and the property inventory of every officer or office of the county which receives or disburses money on behalf of the county or which holds property belonging to the county. Upon the completion of the investigation, the certified public accountant or the state auditor, as the case may be, shall render a report to the county commission. The county commission shall provide for the expense of such audit if made by a certified public accountant employed by the county commission. For audits performed by the state auditor, all expenses incurred in performing the audit, including salaries of auditors, examiners, clerks, and other employees of the state auditor, shall be paid by the county or county commission and the moneys are to be deposited in the petition audit revolving trust fund pursuant to section 29.230.