A property tax appeal asks the county to lower your property's assessed value, the figure your tax bill is calculated from. You do not appeal the bill itself, and the tax rate is not part of it. In Cook County you can appeal every year, not only in your reassessment year, in a filing window set for your township. You can challenge a Cook County assessment at up to three levels, in this order: the Cook County Assessor, the Board of Review, and then the Illinois Property Tax Appeal Board (PTAB) or the Circuit Court. The Assessor is optional, but filing there gives you two chances at a reduction instead of one. Most reductions come from the first two.
How to appeal property taxes in Cook County, step by step
1. Find your township's window
Each of the 38 townships has its own dates, once a year at the Assessor and once at the Board of Review. The Assessor's window opens when it mails the township's assessment notices and stays open for several weeks (about six weeks in 2026). The Board of Review opens each township after the Assessor has finished with it, for about 30 days. Your property's dates are on our deadlines page. If both windows have closed, you can appeal again next year. A Certificate of Error can still correct a factual mistake or a missing exemption from an earlier year.
2. Check your assessment
Your assessment notice, and the Assessor's website, show the Assessor's market value for your property and its assessed value. Homes and apartment buildings are assessed at 10% of market value, and most commercial property at 25%. You have a case if any of these is true: similar properties nearby are assessed lower; the Assessor's market value is higher than the property would sell for; or the county's record of it is wrong, for example its size. Our free property check compares your home with similar homes nearby in under a minute.
3. Gather your evidence
For a home: similar homes nearby with lower assessments, a recent purchase or appraisal below the Assessor's market value, and proof of anything the county has wrong. For commercial and apartment buildings: three years of income and expenses, a current rent roll and the leases. For empty space, proof that it was empty and that you tried to lease it. Both venues ask for a photo of the front of the property; the Board's must have been taken within the last 12 months. If you bought the property recently, you must say so: at the Assessor, a purchase in the two years before January 1 of the appeal year; at the Board of Review, one in the three years before.
4. File at the Assessor
Appeals are filed online while the township's window is open. The Assessor decides on the written evidence, without a hearing. The Assessor decides after your township's window closes, usually within a few weeks to a few months. You do not need an attorney at the Assessor.
5. File at the Board of Review
The Board of Review is independent of the Assessor, and you can file there whether or not the Assessor reduced your assessment. You can also file at the Board if you did not file at the Assessor. Most residential appeals are decided on the written evidence; an owner may ask for a hearing. At the Board of Review and at PTAB, an owner who is a person can file alone. A company, such as an LLC or corporation, must be represented by an attorney, and so must a condominium association appealing for the whole building. The Board of Review decides later the same assessment year, before second-installment bills are issued.
6. After the Board
After the Board of Review decides, you can go to PTAB or to the Circuit Court, not both.
- PTAB, the state's Property Tax Appeal Board. The deadline is 30 days after the Board's written decision. If the Board sends its final results for your township to the Assessor later than that, the 30 days run from that date instead. Filing is free. An owner who is a person can file alone; a company needs an Illinois attorney. PTAB cases often take two years or more, and a reduction is paid back as a refund.
- A tax objection complaint in the Circuit Court of Cook County. Instead of PTAB, you may file a tax objection complaint in the Circuit Court of Cook County. You must pay the full tax within 60 days after the first penalty date of the second installment, and file the complaint within 165 days after that date (35 ILCS 200/23-5, 23-10). If you choose the Circuit Court, you pay the court's filing fee; we tell you the amount before we file. This is a court case.
What you do, and what we do
- You: check your property free on this site, then sign up online.
- We: build the evidence and file your appeal in your township's windows, usually at the Cook County Assessor and then at the Board of Review, and tell you each decision.
- We: if you bought your home recently for at least the Assessor's market value, file at the Board of Review only, and tell you why.
- We: if the Board's decision is still too high, tell you whether an appeal to PTAB, or a tax objection complaint in the Circuit Court, is worth filing; you decide, on the same fee terms.
- If your assessment is reduced, the lower tax shows on your second-installment bill the following year. We invoice our fee, 25% of the first-year savings, after that bill is issued.
- Keep paying your tax bills on time while the appeal is decided. A reduction lowers a later bill; it does not pause the one you have now.
- Next year: you can appeal every year, not only in your reassessment year.
Commercial property: what is different
A commercial assessment is an income calculation. On every file, a CPA checks the valuation and an attorney argues the case, at every level of review. The Assessor values most commercial buildings from the rent they earn and what they cost to run. So the case is built from the building's own records.
What we will ask you for: income and expense statements, last three years; a current rent roll; leases, or a lease summary; a few photographs; anything unusual. For a building you occupy yourself, items 2 and 3 don't apply; we arrange a letter of value instead.
You sign online in about five minutes. We send you a secure link with exactly what your building needs, and you send your records at your pace. Nothing is filed until the attorney has read all of them. If an LLC, corporation or other company owns the property, the Board of Review and PTAB require a licensed attorney to represent it. A company needs an attorney at the Board, and we are its attorneys. The Assessor often sets a new commercial value each year, so many owners appeal every year. A few commercial cases need an appraisal. If yours does, we tell you the cost before anything is ordered, and nothing is ordered without your approval. Our fee is 25% of the first year's savings, and nothing if there is no reduction.
When you will see the savings
An appeal lowers the assessment for the tax year you appeal. Cook County bills each year's tax in the following year, in two installments. The first installment is 55% of the previous year's total tax. The second is figured on the final assessment, after the Assessor and the Board of Review have decided. So a reduction from a 2026 appeal shows on the second-installment bill issued in 2027. If the bill has not been issued yet, it is figured on the lower value. If you have already paid, you get the difference back. A PTAB or Circuit Court reduction is paid as a refund.
For a home, a reduction usually stays in place for the rest of your township's three-year reassessment cycle. The county can change it in a later year, so we review your assessment each year. You can appeal every year, not only in your reassessment year.
How long it takes
| Stage | When you file | When it is decided |
|---|---|---|
| Assessor | In your township's window, about six weeks from the notice | A few weeks to a few months after the window closes |
| Board of Review | About 30 days, after the Assessor has finished your township | Later the same assessment year, before second-installment bills are issued |
| PTAB | Within 30 days of the Board's decision | Often two years or more |
| Circuit Court | Pay the full tax within 60 days, and file within 165 days, of the second installment's first penalty date | On the court's schedule |
Filing yourself or hiring an attorney
Do you need a lawyer? Not if you own the property in your own name: filing is free, and you can file at the Assessor, the Board of Review and PTAB yourself. If a company, such as an LLC or corporation, owns it, or a condominium association appeals for the whole building, the Board of Review and PTAB require an attorney.
The difference is in the work:
| Filing yourself | Hiring us | |
|---|---|---|
| Cost | Filing is free. | 25% of first-year savings, only if your assessment is reduced. |
| Evidence | You find the comparable properties and sales. | Our attorneys and CPAs prepare the evidence. |
| Venues | The Assessor, the Board of Review and PTAB; the Circuit Court if you own the property in your own name. | The Assessor, the Board of Review, PTAB and the Circuit Court. |
| Deadlines | You track each window. | We track the windows and file. |
More on the choice: Why hire Cook County Tax Appeals, LLC instead of filing a property tax appeal yourself? The county's outcome data by venue: Cook County Property Tax Attorney: When Representation Matters. Start with the free property check.
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