55 ILCS 5/6-31005
In addition to any other audit required by this Division, the County Board shall cause an audit to be made of all funds and accounts under the management or control of a county official as soon as possible after such official leaves office for any reason. The audit shall be filed with the county board not later than 180 days after the official leaves office. The audit shall be performed and the audit report shall be prepared and filed with the Chairman of the County Board by an auditor .
As used in this Section, "county official" means any elected county officer or any officer appointed by the county board who is charged with the management or control of any county funds; and "audit" means a post facto examination of books, documents, records, and other evidence relating to the obligation, receipt, expenditure or use of public funds of the county, including governmental operations relating to such obligations, receipt, expenditure or use.
55 ILCS 5/6-31005