March 25, 2026
If you own property in Cook County, your window to appeal your property tax assessment doesn't stay open forever. Each township has its own filing period — and missing the deadline means waiting another year. Here's everything you need to know.
Cook County operates on a triennial (3-year) reassessment cycle, divided into three districts:
Even if your township isn't in the current reassessment year, you can still appeal your existing assessment every year at the Board of Review level. But your strongest window — when the Assessor's Office is actively reviewing values — is during your reassessment year.
The following townships are in the 2026 south district reassessment cycle. Appeal windows typically open 30 days after assessment notices are mailed.
Bloom Township — Chicago Heights, Flossmoor, Glenwood, Homewood, Lansing, Lynwood, Sauk Village, South Chicago Heights, Thornton
Bremen Township — Midlothian, Oak Forest, Tinley Park, Orland Park
Calumet Township — Blue Island, Riverdale, Dolton, Harvey
Rich Township — Matteson, Park Forest, Richton Park, Olympia Fields
Thornton Township — Harvey, Hazel Crest, Homewood, Flossmoor, South Holland
Worth Township — Worth, Palos Hills, Oak Lawn, Chicago Ridge, Alsip
Lemont Township — Lemont, Palos Park, Homer Glen
Lyons Township — Berwyn, Brookfield, LaGrange, Western Springs
Orland Township — Orland Park, Orland Hills, Tinley Park
Palos Township — Palos Heights, Palos Hills, Palos Park, Hickory Hills
Stickney Township — Stickney, Forest View, Bedford Park, Summit
If you're in the north suburbs, your Assessor appeal window has closed for 2025, but you can still appeal at the Board of Review level. Contact the Cook County Board of Review directly at cookcountyboardofreview.com for current BOR filing windows.
Key north townships include: Barrington, Elk Grove, Evanston, Maine, New Trier, Niles, Northfield, Palatine, Wheeling.
Chicago property owners in the 2024 reassessment cycle can also appeal at the Board of Review. The BOR accepts appeals year-round based on its own calendar.
Step 1: Verify your assessed value. Find it on your most recent tax bill or at the Cook County Assessor's website (cookcountyassessor.com).
Step 2: Check for over-assessment. Your assessment should reflect 10% of your property's market value. If comparable homes in your area have sold for significantly less than what your assessment implies, you likely have grounds for an appeal.
Step 3: Gather comparable sales (Rule 15 evidence). The strongest appeal argument is comparable sales data — homes similar to yours that sold recently at lower values. This is called Rule 15 evidence.
Step 4: File before your deadline. Late appeals are not accepted.
The south district townships listed above have appeal windows closing in March 2026. If you haven't checked whether you're over-assessed, now is the time.
Start your free property assessment check at OverTaxed IL — enter your address and we'll pull your current assessment, find comparable sales, and show you whether you have grounds for an appeal. If you do, we generate the full Rule 15-compliant appeal packet automatically.
Deadlines are firm. Five minutes now could save you $1,000+ per year.