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Illinois Property Tax GuideAppeal and Lower Your Illinois Property Tax.
Illinois has the highest effective property tax rate in the country. The average Illinois homeowner pays around $5,400 in property taxes per year, and in Cook County townships the bill can easily exceed $10,000. Appealing is not a luxury, it is basic financial hygiene.
How the Illinois Appeal Process Works
- Watch for your reassessment notice. Cook County reassesses on a triennial rolling schedule; other counties quadrennial.
- First round, Cook County Assessor (or county assessor elsewhere). File online within 30 days of the notice.
- Second round, Board of Review. Open 30 days per township. Accepts a new, stronger case.
- PTAB or circuit court if still denied. Choose one, not both.
Major Illinois Counties, Where to File
- Cook County Assessor: cookcountyassessor.com. Rolling 30 day township windows.
- Cook County Board of Review: cookcountyboardofreview.com. Separate 30 day window after assessor decision.
- DuPage County: dupageco.org/supervisorofassessments. ~30 days after notice.
- Lake County: lakecountyil.gov/assessor. Deadline varies by township.
- Will County: willcountysoa.com. 30 day window.
- Kane County: kanecountyassessments.org. 30 day window.
Cook County is unique. Because Cook has two independent appeal rounds (Assessor, then Board of Review), you effectively get two bites at the apple every assessment cycle. Many homeowners win at the Board of Review after being denied at the Assessor, file both.
When You Probably Qualify for a Reduction
- Your assessed value jumped significantly in a reassessment year
- Similar homes on your block are assessed noticeably lower (lack of uniformity)
- Your home has foundation, roof, plumbing, or other unrepaired issues
- Recent sales of comparable homes undercut your assessment
- Your property has an inaccurate record card (wrong square footage, bedrooms, etc.)
Get an Illinois Appeal Report in 48 Hours
We pull your county record, compute lack of uniformity and market value cases, and produce a filing ready report with comparables for $50 flat.
Start My Illinois Appeal →Illinois Property Tax Appeal FAQ
Will appealing raise my assessment?
No. Illinois law limits appeal outcomes to reductions or no change, never increases.
What is lack of uniformity?
Illinois law requires assessments to be uniform across comparable properties. If similar homes near yours are assessed at a lower level than yours (relative to market value), you have a lack of uniformity case even when market value looks right.
How often can I appeal?
Cook County allows appeals every year. Most other Illinois counties operate on a 4 year reassessment cycle but still accept annual appeals based on new evidence.
Do I need a tax attorney?
No. Homeowner filings are accepted at every stage, Assessor, Board of Review, and PTAB, without representation.