A Cook County tax bill goes up for one of three reasons: your assessment rose (most often in your township's reassessment year), the tax rate rose because local governments raised their levies, or an exemption came off the bill. You can appeal the assessment and claim a missing exemption; the tax rate is set by the local governments that levy the tax.
Your assessment went up
The Assessor revalues every property once every three years, one region at a time: the City of Chicago, the suburbs north of North Avenue, and the suburbs south of North Avenue. In the year your region is reassessed, a rise in your home's estimated market value shows up in full on your second-installment bill. In 2025 the north and northwest suburbs were reassessed: homeowners' taxes there rose 9.9%, and the median homeowner bill rose 6.7%, to $8,007. The south and southwest suburbs are being reassessed for the 2026 tax year.
A higher value is not always wrong, but the Assessor values homes from sales data and models, not visits, so the figure can overstate what yours would sell for, or rest on wrong details such as the square footage. That is what an appeal corrects.
The tax rate went up
Your tax rate is the total of the rates of every local government that taxes your property: the schools, the city or village, the county, the parks and others. When they ask for more money, the rates rise. For the 2025 tax year they asked for $743.8 million more across Cook County, about 3.9%, for a total of more than $19.9 billion: at least the 32nd year in a row the total went up.
Your share also depends on how your value moves against everyone else's. When home values rise faster than commercial values, part of the tax moves from businesses onto homeowners.
An exemption came off
Exemptions lower the value you are taxed on: the Homeowner Exemption takes $10,000 off the equalized value, and the Senior Exemption a further $8,000. If one is missing from this year's bill, because the home changed hands or the Senior Freeze was not re-filed for the year, the bill rises by the tax on that amount. Check the exemptions on your bill first. An exemption you qualified for but did not receive can be claimed for past years through a Certificate of Error.
Why Chicago bills rose
For the 2024 tax year, billed in 2025, the median Chicago homeowner's bill rose a record 16.7%, to $4,457. Chicago was reassessed that year, and the assessed value of commercial property in the Loop fell by about 7.2%; with less tax on downtown buildings, more of it fell on homeowners. On the South and West Sides, where home values had risen fastest, median bills rose more than 30% in 15 community areas.
For the 2025 tax year, with Chicago between reassessments, the median Chicago homeowner's bill rose 3.2%, to $4,597.
What you can do
- Check the details the Assessor has on record for your property: a wrong square footage or a basement you do not have is the easiest thing to correct.
- Appeal the assessment at the Assessor, then the Board of Review, during your township's filing window. You can appeal every year, not only in a reassessment year.
- Claim any missing exemption, and re-file the Senior Freeze every year.
- Pay on time: a pending appeal does not move the due date, and a late payment costs 0.75% a month.
Sources: Cook County Treasurer, 2025 and 2024 Tax Year Bill Analyses.