In a normal year, Cook County's second-installment property tax bill lands around August 1. This year the county announced on June 9 that the bills would be roughly two months late, and reopened a $300 million bridge-loan fund for the school districts and towns waiting on the money. That delay is now resolved: the 1.8 million tax year 2025 second-installment bills went live online on August 18, with paper copies mailing September 1 and payment due October 1.
So if you've been watching the mailbox: nothing was wrong with your account, and the bill was late for everyone. Now that it's out, it's the one that matters — the second installment is where reassessments, rate changes and exemptions all show up. For the north suburbs, reassessed in 2025, this delayed bill is the one carrying the increase.
What's on the Bill
The bill is built around your PIN — a 14-digit Property Index Number tied to the property, not to you. The Treasurer's own analogy: a PIN is to a property what a Social Security number is to a person. It's on your deed and every bill, and it's what you need to look anything up.
Below that, the bill's three main sections:
- "Where Your Money Goes" — every taxing district you pay, with this year's tax next to last year's and the difference. This is the fastest way to see who raised your bill.
- The Tax Calculator box — the arithmetic: assessed value × state equalizer = EAV, × local rate, minus each exemption you received, split into the two installments.
- The district breakdown — each district's rate and share, including how much of your payment goes to its pension obligations. That pension column is the part of the bill almost nobody reads.
Lost the paper copy? The Treasurer's site prints current and prior-year bills free — search by PIN or address.
The Math, Line by Line
Residential property in Cook County is assessed at 10% of market value. That assessed value is multiplied by the state equalizer, which the Illinois Department of Revenue finalized at 3.0300 for tax year 2025 on June 18 — down slightly from 3.0355 the year before. The result is your equalized assessed value, or EAV. Exemptions subtract from the EAV, and your town's composite rate applies to what's left.
On a $400,000 house with the standard homeowner exemption, at an illustrative 8% composite rate:
| Step | Amount |
|---|---|
| Market value | $400,000 |
| Assessed value (10%) | $40,000 |
| × 2025 equalizer (3.0300) | $121,200 EAV |
| − Homeowner exemption | $111,200 |
| × 8% composite rate | $8,896 |
Your rate depends on your town's stack of taxing districts — that's the number that ranges from roughly 6% in the cheapest suburbs to over 14% in the most expensive, and it's the subject of its own guide.
Due Dates, and What Late Costs
Cook County bills in two installments. The first is always 55% of last year's total — it's an estimate, set by state law, and it was due April 1 this year (a date now written into statute). The second installment settles the real amount once rates and assessments are final, which is the bill currently delayed.
For reference, last cycle ran late too: tax year 2024's second-installment bills were mailed in mid-November 2025 and due December 15.
If you pay late, interest accrues at 0.75% per month (9% a year), set by state law for tax year 2023 and later, and printed on the bill itself. (One of the Treasurer's own FAQ pages still says 1.5%; that's the old pre-2023 rate. The statute and the bill control.)
Ways to pay, per the Treasurer: online from a bank account free; online by card with a third-party fee the county doesn't keep; at roughly 400 Chase branches in Illinois with your payment coupon; at 157 community banks if you have an account there; by mail, where the USPS postmark counts as your payment date — postage meters and FedEx don't; or in person at 118 N. Clark St., Room 112.
The Exemptions, and Which Ones Renew Themselves
| Exemption | EAV reduction | Renews automatically? |
|---|---|---|
| Homeowner | $10,000 | Yes |
| Senior (65+) | $8,000 | Yes |
| Senior Freeze (income ≤ $65,000) | freezes EAV | No — file every year |
| Persons with Disabilities | $2,000 | Yes, for prior recipients |
| Returning Veterans | $5,000 | No — file annually |
| Veterans with Disabilities | $2,500 to $250,000 by rating | 100% P&T renews; others file |
| Longtime Homeowner | caps assessment jumps | Assessor mails applications |
The Senior Freeze is the one seniors lose by assuming it renews — it requires a fresh application every year, with 2024 household income of $65,000 or less. And the Longtime Homeowner exemption can't be applied for cold: the Assessor identifies qualifying properties (fewer than 2% of homeowners) and mails applications in April.
Applications for this tax year closed May 15.
Missed an Exemption? You Can Go Back Four Years
A Certificate of Error lets a homeowner claim exemptions that should have applied to already-paid bills for tax years 2021 through 2024. The application runs online through the Assessor with proof you occupied the home as your primary residence on January 1 of the year claimed. The Assessor quotes 8 to 10 weeks to process, plus 3 to 4 weeks for the Treasurer to mail the refund check.
If a senior in your family has been paying without the senior exemptions, this is often four figures of recoverable money.
Appealing: Free, No Lawyer, and the Numbers Favor You
The number that reframes the whole process comes from the Board of Review's own annual report: in tax year 2023, nearly 62% of homeowners who appealed without an attorney won a reduction, out of roughly 248,000 appeals.
There are three layers, and each is free to enter:
The Assessor. Each township's window runs about 30 days from its reassessment notice; the office says an online appeal takes as little as 20 minutes. For uniformity appeals you don't need to hunt your own comparable properties — the Assessor's analysts check comps for you. You can appeal in non-reassessment years too.
The Board of Review. A separate, later window, and you're at no disadvantage arriving fresh — the Board's own FAQ says skipping the Assessor level costs you nothing. Photos of your property are required; comparables help. An attorney is only mandatory when the property is held by a corporation or LLC. The Board opened pre-filing for its 2026 session on July 20.
PTAB. After the Board, the state Property Tax Appeal Board takes filings within 30 days of the Board's decision postmark, no filing fee, self-representation allowed.
Timing, as of August 24: the south and west suburbs are being reassessed this year. The Cicero and Stickney Assessor windows have both closed; Stickney's last filing date was August 12. Lyons is open through September 3, Bremen through September 24 and Lemont through September 29, per the Assessor's own calendar, with Worth, Orland and Thornton still to open. If your notice arrived this summer, the clock printed on it is real. The rest of them, including the townships with no date posted at all, sit on our Chicagoland deadline calendar.
Takeaway: the delayed bill arriving this fall is the one carrying reassessments — check the exemption lines before you pay, because a missing one is recoverable four years back, and an appeal is free with roughly 62% of self-represented homeowners winning something.
Every figure above comes from the Cook County Treasurer, Assessor, Board of Review, PTAB, or the Illinois Department of Revenue, checked in late July 2026, with the appeal windows re-checked against the Assessor on August 24. The second-installment due date was announced August 18, 2026: bills online that day, mailed September 1, due October 1.
This guide is part of The First-Time Buyer's Suburban Starter Pack.