35 ILCS 200/20-100
In counties with 3,000,000 or more inhabitants, when any special assessment made by any city, incorporated town or village, under its charter, or by any corporate authorities, commissioners or persons, pursuant to law, remains unpaid in whole or in part, return thereof shall be made to the county collector on or before the first day of August next after it became payable, in the same manner as returns are made for delinquent property tax.
The subsequent advertisement, judgment and sale of property on account of delinquent special assessments, as provided below, shall be considered supplemental to but also a part of the sale of delinquent general taxes of the year in which the judgment and sale on account of delinquent special assessments is ordered. The penalties provided by law shall attach to both general taxes and special assessments in the same manner as if there were only one judgment and order of sale.
In cases where application for judgment and order of sale for special assessments, special taxes, or installments thereof, and interest, may be made under Section 21-155, notwithstanding that the special assessments, special taxes, or installments, and interest, have not been returned as delinquent to the county collector on or before the first day of August in the year in which application is made, and notwithstanding that the assessments, taxes, installments and interest, were not marked on the general tax books of the county collector on or before the tenth day of March of the same year, or within 15 days after the county collector received the general tax books in that year, the advertisement, judgment and order of sale for delinquent special assessments, special taxes, or installments thereof, and interest, need not be subsequent to or regarded as supplemental to or as a part of the sale on account of delinquent general taxes of the year in which such separate advertisement, judgment and order of sale on account of delinquent special assessments, special taxes, or installments thereof, and interest, is had. However, the penalties provided by law shall attach to the special assessments, special taxes, or installments thereof, and interest, in the same manner as if there were only one judgment and order of sale. County collectors shall collect, account for, and pay over the special assessments, special taxes, or installments to the authorities or persons having authority to receive them, in the same manner as they are required to collect, account for, and pay over taxes.
Upon return of delinquent special assessments to the county collector, he or she may transfer the amounts stated on the returns to the tax books, setting down opposite the respective properties, in proper columns, the amounts assessed against each property.
35 ILCS 200/20-100