35 ILCS 200/21-155
In counties with 3,000,000 or more inhabitants, the application for judgment upon delinquent special assessments or special taxes in each year shall include only special assessments, special taxes, or installments thereof, and interest, as are returned as delinquent to the county collector on or before August 1 in the year in which the application is made, and in the case of those levied upon property in any city with 1,000,000 or more inhabitants, as were marked on the general tax books of the county collector on or before March 10 of the same year or within 15 days after the county collector received the general tax books that year. The judgment of sale shall include interest on matured installments up to the date of the judgment.
In the 10 years following the completion of a general reassessment in any county with 3,000,000 or more inhabitants, made under an order of the Department, the application shall be made during the month of October for judgment and order of sale for special assessments, special taxes, or installments thereof, and interest, in each year on delinquent properties, notwithstanding that such special assessments, special taxes, or installments thereof, and interest are not returned as delinquent to the county collector, on or before August 1 in the year in which the application is made, and in the case of those levied upon property in any city with 1,000,000 or more inhabitants, notwithstanding that such special assessments, special taxes or installments thereof, and interest, were not marked on the general tax books of the county collector, on or before March 10 of the same year or within 15 days after the county collector received the general tax books in that year, in that case, the county collector shall include in the application all special assessments, special taxes, and installments thereof, and interest, then remaining unpaid. Within 30 days after the county collector has received the general tax books, the special assessments, special taxes, or installments thereof, and interest, then remaining unpaid, shall be marked therein. If for any reason, the application cannot be made during the month of October, it shall be made at any time not later than January 1.
35 ILCS 200/21-155