When Are Property Taxes Due in Illinois: Cook and 101 Counties

Property taxes in Illinois are due in two installments each year, and the dates depend on your county. If you live anywhere outside Cook County, the first installment is due June 1 and the second is due September 1. In Cook County, the first installment is always due March 1, and the second installment arrives later in the year once final rates are set. Illinois bills you a year behind, so the bills arriving in 2026 cover your 2025 taxes.

Due Dates in the 101 Counties Outside Cook

For property anywhere in Illinois outside Cook County, the first installment becomes delinquent if unpaid by June 1, and the second becomes delinquent if unpaid by September 1.1Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/21-15 – General Tax Due Dates Your bill may show a slightly different date if the county board shifted the deadline by ordinance, but those two dates are the statewide baseline.

County boards also have the option to adopt an accelerated estimated billing method similar to the one Cook County uses, though few do. Where a county uses estimated billing for overlapping taxing districts, the first installment bill goes out by May 1 and any adjustments appear on the second installment once final numbers are certified.2Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200 – Property Tax Code The actual dollar amount and the exact date are always printed on the bill your county treasurer mails you.

Due Dates in Cook County

Cook County runs on a faster clock. The first installment is always due March 1 and equals 55% of the total tax you paid the prior year.3Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/21-30 – Accelerated Billing That first bill is an estimate, not the final number. The county needs revenue flowing before the assessment process wraps up, so it bases the March bill on last year’s total.

The second installment covers whatever balance remains after the first payment is subtracted from the actual tax owed. By law, Cook County must prepare and mail those bills by June 30, but the payment deadline shifts each year depending on when final rates are certified.3Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/21-30 – Accelerated Billing In practice, the second installment typically lands in late summer or fall. The Cook County Treasurer’s website posts the exact due date once it’s set, so check there each year rather than assuming a fixed calendar date.

Cook County also has a statutory option to split the tax into four installments instead of two. Under that approach, the first three installments would each equal 25% of the prior year’s total, with the fourth covering the remaining balance. Whether the county board activates this option varies, so watch for announcements from the Treasurer’s office.

How to Find Your Bill and Pay It

Your county treasurer mails the bill to the address on file, and most counties also post bills online. To look up your bill you’ll need your Property Index Number, a unique identifier printed on your tax bill, your deed, and your assessment notices. In Cook County, the PIN is 14 digits.4Cook County Assessor’s Office. Where Do I Find My PIN Other counties use similar numbers and most let you search by owner name or property address.

Each installment comes with its own coupon showing the exact amount and due date. Common payment options include:

  • Mail a check postmarked on or before the due date. Illinois treats the postmark as the payment date.
  • Pay in person at the county treasurer’s office or at participating local banks.
  • Pay online by e-check, typically for a flat processing fee of about $1.00.
  • Pay online by credit or debit card, with a convenience fee generally running from about 2.25% to 2.65% depending on the county.

On a $6,000 bill, the credit card fee alone can run $135 to $160. For a large bill the e-check option saves real money.

Penalties If You Miss the Deadline

Interest starts accruing the day after your due date, and the rate depends on where the property is located.

Even one day late triggers a full month’s charge. If you owe $5,000 in a non-Cook county, being one day late costs $75. Being three months late costs $225, and it compounds from there. If you can’t pay the full amount, a partial payment before the deadline still cuts the base the penalty is calculated against.

If a Mortgage Escrow Account Pays Your Bill

If you have a mortgage with an escrow account, your lender collects a portion of your estimated taxes with each monthly payment and is supposed to forward it to the county. Federal rules require the servicer to pay each escrow disbursement before the penalty deadline, as long as your mortgage payment is no more than 30 days overdue.5Consumer Financial Protection Bureau. Escrow Accounts

You are still legally responsible for the tax even when a lender handles the payment. If the mortgage company misses the deadline, pays the wrong amount, or pays on the wrong PIN, penalties and interest still attach to your property. The Cook County Treasurer’s office reports this happens to more than 2,500 taxpayers each year in Cook County alone.6Cook County Treasurer’s Office. Monitoring Your Mortgage After each installment deadline passes, check your county treasurer’s website to confirm the payment posted correctly. If the lender caused the late payment, state and federal laws require the lender to cover the interest and fees, but you have to catch the error first.

What Happens If the Bill Stays Unpaid

When property taxes go unpaid long enough, the county sells the delinquent tax debt. A third-party buyer pays what you owe, a lien attaches to your property, and a redemption period starts running during which you must pay the buyer back, with interest, to clear the lien. You don’t lose ownership immediately, but you do lose it if the clock runs out.

The redemption window depends on the type of property:

Miss the redemption deadline and the tax buyer can petition for a deed to your property. The amount you’d owe to redeem includes the original taxes plus accumulated penalties, the buyer’s costs, and additional statutory interest. For owners of commercial or vacant land, the one-year window is short enough that a single bad year of oversight can lead to real trouble.