March 25, 2026
Cook County property taxes confuse even longtime homeowners. The system has multiple layers — assessments, equalization factors, exemptions, and appeals — each of which affects your final bill.
Here's how it actually works.
The Cook County Assessor's Office estimates the market value of every property in the county on a rotating three-year cycle. Your assessed value is set at approximately 10% of that estimated market value.
For example: if your home is valued at $350,000, your assessed value would be around $35,000.
This is where mistakes happen. Assessors use mass appraisal methods — they can't inspect every property individually. Errors are common.
Illinois applies an equalization factor (also called the multiplier) to bring assessed values in line with state standards. For Cook County, this factor changes annually. It's applied to your assessed value before taxes are calculated.
Illinois offers several exemptions that reduce your taxable value:
Make sure you're claiming all exemptions you qualify for — unclaimed exemptions are free money left on the table.
Your county, city, township, school district, and other local bodies each set their own tax rates. These rates are applied to your equalized assessed value (after exemptions) to produce your tax bill.
Cook County issues two tax bills per year: the first installment (due March) and the second installment (due August).
Assessment appeal: Filed with the Cook County Assessor during your township's appeal window. This is the most impactful step — reductions here carry forward.
Board of Review appeal: A second chance if you're unsatisfied with the Assessor's decision.
Illinois Property Tax Appeal Board (PTAB): State-level appeal for larger discrepancies.
Most homeowners pay whatever bill arrives. But the assessment process is imperfect, and appealing is free. If your assessed value is out of line with comparable properties, you have strong grounds for a reduction.
Start with a free check at overtaxed-il.com/check to see where you stand.