35 ILCS 200/13-10
Whenever it appears to the Department that the property in any county, or in any assessment district, has not been assessed in substantial compliance with law, the Department may, in its discretion, in any year, either before or after the original assessment is completed by the local assessment officers, order a reassessment by the local assessing officers for that year of all or any class of the taxable property in the county or assessment district. The reassessment shall be substituted for the original assessment. The order directing a reassessment shall be filed in the office of the county treasurer of the county in which the reassessment has been ordered, except in counties having an elective board of review or board of appeals in which case the order shall be filed with that board.
If any general assessment is not published in any year for which the assessment was made, or if that publication was not made in time to permit the examination thereof by the Department in that year, the Department may in any of the 3 years intervening between the years for which general assessments are made, order reassessment of the last general assessment of all or any class of property in the county or assessment district, and the reassessment shall be substituted for the original general assessment for the intervening year and thereafter until the next general assessment is made.
No substitute assessment shall invalidate any prior assessment as to taxes extended thereon.
The Department may order the board of review of any county not having an elected county assessor and an elective board of review to convene in extraordinary session for the purpose of further revising, correcting and equalizing the assessment of property within that county.
When a reassessment has been ordered under this Section, the individual assessments made under such order shall be reviewed, revised and corrected by townships or taxing districts by the assessors making the reassessment.
The assessors making the reassessment shall give notice of the order under which it is made showing the class of property affected by the reassessment, each township or taxing district to be reviewed, revised and corrected and the time and place for the revision and correction, by publishing the notice in one or more newspapers, published and having a general circulation in the county, at least 5 days before the time set for the revision in each township or taxing district.
35 ILCS 200/13-10