35 ILCS 515/9
For taxable years prior to 2003, if any local services tax, or part thereof, imposed by this Act is not paid on or before the due date for such tax, interest on such amount at the rate of 1 1/2% per month shall be paid for the period from such due date to the date of payment of such amount. Except as otherwise provided in this Section, for taxable year 2003 and thereafter, if any local services tax, or part thereof, imposed by this Act is not paid on or before the due date for such tax, the taxpayer shall be required to pay a penalty of $25 per month, or any portion thereof, not to exceed $100. In counties with a population of more than 700,000 and less than 900,000, if any local services tax, or part thereof, imposed by this Act is not paid on or before the due date for such tax, the taxpayer shall be required to pay a penalty of $25 per month, or any portion thereof, not to exceed the lesser of (i) $100 or (ii) 50% of the original tax imposed. In all counties, if such failure to pay such tax is the result of fraud, there shall be added to the tax as a penalty an amount equal to 50% of the deficiency.
35 ILCS 515/9