Why did your Cook County tax bill go up?

Your bill has four moving parts

The Assessor says your bill "depends not just on your property's assessment, but also its exemptions, the total assessed value of your community, and the levies passed by local taxing bodies."

In practice, the bill is your assessed value times the state equalizer, minus your exemptions, times your local tax rate. Any one of those can change from year to year. Our calculator shows how they fit together.

The Assessor also stresses that it "does not set property tax levies, rates, or bills."

Which bill are you looking at?

Cook County bills come in two installments. The first is, by law, 55% of the previous year's total bill and is due March 1.

The second installment is where the current year's values, exemptions and rates show up. For tax year 2025, the Treasurer mailed second-installment bills on September 1, 2026, due by October 1, 2026.

So if your second installment felt large, part of the reason can be the split itself. Compare full-year totals, not single installments.

Reason 1: local levies and tax rates

Each taxing district, such as your school district, city or village, county and parks, files a levy with the Cook County Clerk. The Clerk then sets the rate needed per $100 of taxable value to raise that money from all property in the district.

The Clerk notes that state law can limit some increases through maximum rates and "tax caps," but those limits do not apply to money needed to pay bonds and certain other charges.

Your bill lists every district funded by your taxes. The Treasurer's site also shows the debt and pensions of local taxing bodies attributed to your property.

Reason 2: your share of the community’s value

The Assessor explains that your share of the total assessed value in your community sets your share of its taxes. "If other properties' assessments increase more than yours, this can shrink your home's share of property taxes."

The reverse is also possible. Your home's value can stay the same while its share of the tax bill moves.

Reason 3: the state equalizer

Every assessed value in Cook County is multiplied by a state equalizer. The Clerk's figures are 3.0163 for 2023, 3.0355 for 2024 and 3.0300 for 2025.

The Clerk describes the 2025 change as a decrease of 0.18%. So for the bill due October 1, 2026, the equalizer was slightly lower than the year before, not a cause of an increase.

The 2026 equalizer has not been announced yet.

Reason 4: an exemption dropped off

Exemptions lower your equalized assessed value, so losing one can raise your bill noticeably. Check whether each one you expect is still on your bill.

• Senior Freeze: must be filed every year. It freezes your EAV, not your bill, so rates can still push the bill higher.
• Homeowner exemption ($10,000 of EAV): renews automatically as long as your residency stays the same.
• Senior exemption ($8,000 of EAV): renews automatically once applied.

If an exemption you qualified for was missing, the Assessor's Certificate of Error process may give you a refund. See our missed exemption guide.

Reason 5: reassessment, but not in 2026 for Chicago and the north suburbs

Every Cook County property is reassessed once every three years, by township. The Assessor's calendar says the south and west suburbs are being reassessed in 2026.

Properties in the north suburbs and the City of Chicago are not being reassessed in 2026, unless a property had division work, permit applications or other special changes. For them, a 2026 reassessment is not the reason a bill changed.

Reassessment effects reach your bill with a delay. The Assessor says they appear on the second-installment bill the year after the reassessment, so south and west suburban 2026 values will affect bills issued in 2027.

The Assessor's archive lists 2025 as the north suburbs' cycle and 2024 as the City of Chicago's. Outside a reassessment year, the Board of Review says an assessment may change because of occupancy, new construction or other factors.

How the parts add up: two examples

These are made-up round numbers to show the mechanics, not real bills. Example: taxable EAV of $65,750 and a tax rate of 7.000% gives $4,602.50.

Rate change only. If the example rate moves to 7.350% and nothing else changes, the tax becomes about $4,832.63. The home's value did not change at all.

Lost exemption only. If the $10,000 homeowner exemption drops off, taxable EAV becomes $75,750 and the tax about $5,302.50. That is $700 more at the same rate.

Real bills often have several of these at once, which is why comparing each line matters.

What an appeal can and cannot fix

An appeal only reviews your assessment. The Assessor says it "is intended to correct the accuracy of your property's assessment," and PTAB states it has no power to review the amount of a tax bill or the tax rate.

So an appeal cannot undo a higher levy or rate. It can help if your assessed value is out of line with similar homes, too high for the market, or based on wrong facts.

Chicago and north suburban owners can still appeal in 2026 even without a reassessment. A lower assessment may lower a future bill, but not by the same percentage, and appeals can end with no change. Check your home free to see how your assessment compares.

How to check your own bill

1. Download your last two bills from the Treasurer's property tax overview.
2. Compare full-year totals, not one installment against another.
3. Compare the values, exemptions and tax rate printed on each bill to see which one moved.
4. Look at the taxing district lines to see which districts changed the most.
5. Check that every exemption you expect is still listed. If one is missing but you qualified, ask the Assessor about a Certificate of Error.
6. For rate history, the Cook County Clerk publishes yearly tax rate reports and a 10-year summary of rates by tax code.
7. If the assessment itself looks off, see how to appeal and check your township's window on our deadlines page.