55 ILCS 5/3-10020
If any county treasurer shall neglect or refuse to render an account, or make settlement at any time when required by law, or refuse to answer any question regarding the operation of the county treasurer's office propounded to him by the county board, or refuse to provide the county board with any requested information concerning the accounts maintained by the county treasurer's office, provided the requests are for information that the county treasurer is required by law to maintain and in a format already maintained by the county treasurer, or is a defaulter, and in arrears with the county, or is guilty of any other misconduct in his office, the county board may remove him from office, and the presiding officer of the county board, with the advice and consent of the county board, may appoint some suitable person to perform the duties of treasurer until his successor is elected, or appointed and qualified; or if by reason of the death or resignation of the county treasurer, or other cause, the said office shall become vacant, then the vacancy shall be filled as provided in The Election Code by appointment of some suitable person to perform the duties of treasurer, until a county treasurer is elected or appointed and qualified. Provided, that in case any county treasurer is called into the active military service of the United States, the appointee shall perform and discharge all the duties of the county treasurer in such county during the time such county treasurer is in the active military service of the United States, and such county treasurer so appointed shall possess all the powers and discharge all the duties of a regularly elected county treasurer under the laws of this State, and shall be paid the same compensation as provided by law for the county treasurer of the county, apportioned as to the time of service, and such appointment and all authority thereunder shall cease upon the discharge of said county treasurer from such active military service of the United States; and provided further, that the office of county treasurer shall not be deemed to be vacant during the time the said county treasurer is in the active military service of the United States. The person so appointed, shall give bond and security, as required by law of the county treasurer.
55 ILCS 5/3-10020