1.8 Million Cook County Tax Bills Land Tuesday. Here's the 10-Minute Check Worth About $950.

On Tuesday, September 1, the Cook County Treasurer mails out 1.8 million second-installment property tax bills for Tax Year 2025. They're due October 1. If you're impatient, you don't have to wait for the mail carrier — the bills have been viewable online since August 18.

That's a 30-day turnaround on the bigger of your two annual bills, arriving two months later than the usual August 1 schedule. The county's explanation is that last year's overhaul of the technology behind the property tax system pushed everything back, and the delay cascaded forward into this cycle.

Most people are going to open that envelope, make a face, and pay it. Which is a perfectly reasonable plan. But there are four things worth checking first — and one of them is worth roughly $950 a year.

1. Check your exemptions before you check the total

The Homeowner Exemption saves the average Cook County property owner about $950 per year, according to the Assessor's Office. Your exemptions are printed right on the bill. If one isn't listed, it wasn't applied — and you paid full freight.

The people who most often lose an exemption without realizing it:

• Recent buyers. The exemption belongs to the owner, not the house. It does not ride along with the deed. If you bought in the last year or two, this is the single most common miss.

• Seniors on the Senior Freeze. The Low-Income Senior Assessment Freeze does not auto-renew — it has to be filed every single year. Board of Review chair George Cardenas made a point of this last week: seniors fall off the list, and they usually don't find out until the bill shows up.

• Veterans and homeowners with disabilities. Several of these — Returning Veterans, Veterans with Disabilities, the Senior Freeze — require an annual filing rather than renewing on their own.

If something's missing, the fix is a Certificate of Error, which lets you go back and redeem savings from prior years. As of right now, the Assessor's site shows the Homeowner Exemption redeemable for tax years 2021 through 2025, and most of the others for 2021 through 2024. The normal filing window has closed, so applications are processed as Certificates of Error.

One more that nobody applies for because nobody has to: the Home Improvement Exemption shields up to $75,000 of added value for up to four years after you improve the property. It's applied automatically. If you put on an addition and your assessment didn't move much, that's why.

2. This bill is not your appeal — and the date that actually matters is also September 1

Here's the part that trips people up every year. The tax bill is the end of the process. By the time it's in your hand, the assessment behind it was set, appealed, equalized, and multiplied by rates that a few dozen local taxing districts already finalized. You can't appeal the bill. You appeal the assessment, and that happens on a different calendar.

Cook County gives you two shots at it: the Assessor's Office, during your township's 30-business-day window after reassessment notices go out, and the Board of Review, which takes one appeal per PIN per year whether or not you went to the Assessor first.

Which brings us to the other September 1 deadline. For Evanston, New Trier, Norwood Park, Oak Park, River Forest, Riverside and Rogers Park townships, September 1 is the deadline to file a Board of Review appeal aimed at next year's bill, with supporting evidence due September 11. September 1 is also the exemption filing deadline for the first installment of 2026 bills.

And there's a wrinkle specific to this year. After a summer of storms — Governor Pritzker signed a disaster proclamation on August 18 — the Board of Review has opened prefiling and says documented storm damage can be reflected on 2027 bills. Commissioner Larry Rogers advised holding onto interior and exterior photos, insurance information, repair estimates, hotel receipts and contractor reports. Damage that didn't make the home unlivable can still count; garage damage was specifically mentioned. Each case gets handled individually.

Worth being clear about: storm relief is not available on the bill arriving Tuesday. That ship sailed. This is about next year.

3. If you can't pay all of it by October 1, the math changed

A lot of websites still say Illinois charges 1.5% per month, or 18% a year, on late property taxes. That figure is out of date. A state law change cut it in half: late interest is now 0.75% per month, 9% a year. That's printed right on the payment coupon of the bill itself. The Treasurer's office put the savings at about $90 per year for every $1,000 owed. Partial payments are accepted.

None of which is an argument for paying late. Interest is still interest, and unpaid taxes eventually land in the annual tax sale. But if you're staring at a bill you can only partly cover, it's useful to know the actual number rather than the one Google hands you.

4. If your mortgage company pays it, you're not off the hook

Roughly speaking, if you escrow, two things happen after a bigger-than-expected bill. Your servicer pays it, then runs an escrow analysis, and your monthly payment goes up — usually by the increase itself plus a shortage spread over the following twelve months. That notice tends to arrive quietly and get filed under "deal with later."

The second thing: verify it actually got paid, and don't pay it yourself on top. Duplicate payments — homeowner and servicer both paying, or a payoff and a refinance crossing paths — are one of the more routine reasons money ends up sitting at the Treasurer's office waiting to be claimed.

Buying or selling this fall? September 1 moves a real number in your contract

This is where the timing gets interesting, and where most of the money is.

Illinois property taxes are paid in arrears — the bill you get in 2026 covers 2025. So at closing, the seller credits the buyer for the portion of the year the seller owned the home but hasn't been billed for yet. That credit is calculated off the most recent full-year bill, multiplied by a negotiated percentage. In Cook County, 105% to 110% is the common range, and on a $10,000 tax bill the difference between 100% and 110% is about $1,000 out of the seller's pocket.

Here's the timing part. Until this week, the most recent complete bill anyone could negotiate from was Tax Year 2024. As of September 1, there's a fresh Tax Year 2025 number on the table. Contracts written before and after that date may be working off different baselines — worth a conversation with your attorney if you're mid-transaction.

And the trap that costs buyers real money: if the seller has a Senior Exemption, a Senior Freeze, or a veterans exemption, their bill is artificially low compared to what yours will be. Those exemptions leave with the seller. A proration calculated off an exempted bill can fall thousands short of your first real one. The Assessor's property search will show you exactly which exemptions are on a property before you write the offer. It takes about two minutes and I do it on every deal.

Related: pull the actual bill, not a listing site's tax estimate. Those estimates are frequently pulling stale or exemption-inclusive figures.

What this bill does not tell you

This is a Tax Year 2025 bill. It does not reflect the 2026 reassessment of the south and southwest suburban townships — those new values show up on bills issued in 2027. And Chicago's next reassessment is scheduled for 2027, landing on bills in 2028.

So a rough number Tuesday isn't a forecast, and a friendly one isn't a promise.

A few honest caveats

• Nobody can tell you what your next bill will be. Not me, not your neighbor, not the guy on Nextdoor. A tax bill depends on your assessment, the state equalization factor, and levies set by every district that touches your parcel. Those aren't final until they're final.

• A successful appeal doesn't cut your bill by the same percentage. Appeals reduce Equalized Assessed Value. The EAV isn't your tax bill, and the relationship between a reduction and a dollar amount depends on your local rate that year.

• Whether next cycle runs on time is an open question. The county has said it's working to get bills back on schedule. Two consecutive delayed years is the record so far.

If a sale is anywhere in your next twelve months

The tax bill is one of the first three things a buyer's agent looks at, right behind price and days on market. Knowing your real number — and confirming your exemptions are actually on it — is worth doing before the sign goes in the yard, not during attorney review.

I'm happy to pull your bill, check your exemption history, and give you a straight read on what your home is worth in today's market. No cost, no obligation, no pitch at the end of it.

And when you are ready to list: my listing commission is 1.25%, with full service behind it — professional photography, 3D Matterport tours, and full online marketing. My Zero Commission Clause means you owe nothing if you find your own buyer, and you can cancel the agreement at any time.

Jason RosenbergThe Rosenberg Group @ Infiniti Properties312.882.9797https://www.jasonrosenbergrealestate.com/

Related reading: Fritz Kaegi just priced your house. Pat Hynes will send you the bill.

Sources

• Cook County Government, "Cook County Second Installment Property Tax Bills Expected to be Released by September 1, Due October 1," August 18, 2026 — cookcountyil.gov

• Cook County Assessor's Office, "Property Tax Exemptions" (Homeowner Exemption average savings, Certificate of Error tax years, Senior Freeze and Home Improvement Exemption rules) — cookcountyassessoril.gov/exemptions

• WBEZ / Chicago Sun-Times, Violet Miller, "Cook County Board of Review urges residents to start appeals for 2026 tax bills after recent storm damage," August 20, 2026 — wbez.org

• Cook County Treasurer, downloadable tax bill payment coupon (late interest stated at 0.75% per month by state law) — cookcountytreasurer.com

• Chicago Sun-Times, "Cook County cuts yearly interest rate penalty for paying property taxes late in half" (18% to 9% annually; 1.5% to 0.75% monthly) — chicago.suntimes.com

• Cook County Board of Review, township dates and deadlines — cookcountyboardofreview.com

• Illinois tax proration practice (105%–110% Cook County convention, arrears billing): Emalfarb Law LLC, Younis Law Group, and Vesta Preferred proration guides, 2026

This article is general information about the Cook County property tax process, not legal, tax, or financial advice. Confirm all dates and deadlines with the Cook County Treasurer, Assessor, and Board of Review directly, and consult your attorney on anything involving a contract.