40 ILCS 5/21-112

For failure to make timely reporting of employee wages and payment of contributions on covered wages paid prior to January 1, 1987 in accordance with State Agency regulations, a delinquent political subdivision or retirement system may be assessed a late filing penalty which shall be, upon receipt of notice, immediately due and payable to the State Agency. The amount of the penalty may be adjusted from time to time with the approval of the Board of Trustees of the State Employees' Retirement System of Illinois. If the late filing is of such duration that the State Agency is unable to make timely payment on behalf of the political subdivision or retirement system to the U.S. Department of Health and Human Services and a federal interest charge arises, the late filing penalty shall be applied toward payment of the federal interest charge. If the federal interest charge exceeds the amount of the late filing penalty, the political subdivision or retirement system shall be assessed the balance of the federal interest charge.