Browse source-reviewed property tax appeal guides for Illinois. County deadlines, filing methods, and available records can differ by county and tax year.
Each published guide identifies the public sources used for its deadline and filing summary. Confirm current requirements with the official filing authority before submitting anything.
Cook County: 2026 deadline guidance is Township-specific 2026 filing dates; check the live CCAO calendar and your assessment notice. Guide: https://fairpath.app/property-tax-appeal/illinois/cook-county
DuPage County: 2026 deadline guidance is Township-specific 2026 window; verify the publication date and Board of Review deadline. Guide: https://fairpath.app/property-tax-appeal/illinois/dupage-county
Source: Cook County Assessor's Office, Assessment & Appeal Calendar and Deadlines, https://www.cookcountyassessoril.gov/assessment-calendar-and-deadlines. Reviewed 2026-07-15.
Source: Cook County Assessor's Office, Cook County Assessor Advanced Property Search, https://www.cookcountyassessoril.gov/advanced-search. Reviewed 2026-07-15.
Source: Cook County Assessor's Office, Official Appeal Rules of the Cook County Assessor for 2026, https://www.cookcountyassessoril.gov/official-appeal-rules-cook-county-assessor. Reviewed 2026-07-15.
Source: Cook County Assessor's Office, Online Appeals, https://www.cookcountyassessoril.gov/online-appeals. Reviewed 2026-07-15.
Source: Cook County Assessor's Office, Residential Appeals, https://www.cookcountyassessoril.gov/residential-appeals. Reviewed 2026-07-15.
Source: Cook County Board of Review, Residential Assessment Appeals, https://www.cookcountyboardofreview.com/assessment-appeals/residential. Reviewed 2026-07-15.
Source: DuPage County GIS, How to Use the DuPage Parcel Viewer, https://videos.dupagecounty.gov/GIS/HowToUseParcelViewer.pdf. Reviewed 2026-07-15.
Source: DuPage County GIS, Real Estate Database Information, https://www.dupagecounty.gov/GIS/Documents/DuPageCountyRealEstateDatabaseInfo.pdf. Reviewed 2026-07-15.
Source: DuPage County Supervisor of Assessments, Assessment Appeals, https://www.dupagecounty.gov/elected_officials/supervisor_of_assessments/assessment_appeals.php. Reviewed 2026-07-15.
Source: Illinois Department of Revenue, Property Assessment Appeals, https://tax.illinois.gov/localgovernments/property/appeals.html. Reviewed 2026-07-15.