Cook County property tax bills come out in two installments each year. The first installment is mailed by late January with a statutory due date of March 1, and the second installment targets August 1 but almost always arrives late. The 2025 second installment, for example, wasn’t due until December 15. If you’re trying to plan around a specific bill, the actual mailing dates matter more than the statutory targets, because the second installment depends on a chain of agencies finishing their work before any bill can be printed.
First Installment: Late January Mailing, March 1 Due Date
Illinois law requires the Cook County Treasurer to prepare and mail the first installment bill by January 31 each year under 35 ILCS 200/21-30.1Illinois General Assembly. 35 ILCS 200/21-30 – Accelerated Billing The statutory delinquency date is March 1, meaning interest starts accruing on unpaid balances after that date.2Illinois General Assembly. 35 ILCS 200/21-25 – Due Dates Accelerated Billing in Counties of 3,000,000 or More The due date printed on your bill occasionally shifts a few weeks. The 2025 first installment was due April 1 rather than March 1.3Cook County. Pay Property Taxes
The amount is predictable. The first installment is a flat 55% of your previous year’s total tax, so new assessments, rate changes, and exemptions don’t affect it. All of those adjustments land on the second installment instead.4Cook County Assessor’s Office. Your Assessment Notice and Tax Bill
Second Installment: August 1 Target, Often Months Later
The official target for the second installment is August 1, and Cook County misses that date more often than it hits it. The 2024 second installment landed on August 1. The 2025 second installment wasn’t due until December 15. There’s no reliable way to predict which year will be on time and which will slip.
The reason is structural. Before the Treasurer can print a second installment bill, four other agencies have to finish their work in sequence:
- The Cook County Assessor’s Office has to publish valuations for the county’s roughly 1.8 million parcels.
- The Board of Review has to resolve the tens of thousands of assessment appeals filed in response. Until an appeal is decided, the final tax on that property can’t be calculated.
- The Illinois Department of Revenue has to set the equalization factor, or multiplier, that aligns Cook County assessments with the statewide standard.
- The County Clerk then has to calculate tax rates for each of the hundreds of taxing districts within the county.
A delay at any step pushes everything downstream. That is why the second installment can arrive anywhere from August through December depending on the year.
How to Check Whether Your Bill Has Been Issued
Because the second installment is unpredictable, the best way to track your bill is to check the Cook County Property Tax Portal at cookcountypropertyinfo.com rather than waiting for mail. Enter your 14-digit Property Index Number (PIN) or your property address to pull up the account.5Cook County Property Tax Portal. Cook County Property Tax Portal Your PIN appears on prior tax bills, assessment notices, and your deed. The portal shows whether a bill has been generated, the amount owed, and whether any payment has posted.
The Treasurer’s Office also offers eBilling, which replaces your paper bill with an email notification once you sign up.6Cook County Treasurer’s Office. Sign Up for eBilling Checking the portal every few weeks between July and December is a reasonable habit during years when the second installment is running late.
The 30-Day Mailing Rule
Whenever a bill does go out, Illinois law requires that it be mailed at least 30 days before the date unpaid taxes become delinquent.7Justia Law. Illinois Compiled Statutes 35 ILCS 200 Title 7 – Tax Collection So once you see a bill posted online or arrive in the mail, you have at least a month to pay before penalties start. The exact due date is printed on the face of the bill.
Not receiving a bill does not excuse payment. You remain legally responsible for your property taxes whether or not the physical bill reaches you. If a due date is approaching and nothing has arrived, check the portal or call the Treasurer’s Office at (312) 443-5100 to confirm your balance.
What Happens If You Pay Late
Starting with tax year 2023, late-payment interest on Cook County property taxes was cut in half. Unpaid balances now accrue at 0.75% per month, or 9% annually, down from the old 1.5% per month (18% annually).2Illinois General Assembly. 35 ILCS 200/21-25 – Due Dates Accelerated Billing in Counties of 3,000,000 or More Interest applies to any portion of a month, so being one day late costs the same as being 29 days late within that month.8Cook County Treasurer’s Office. Cook County Treasurer News
The old 1.5% rate still applies to taxes owed for tax years before 2023. If you have a lingering unpaid balance from 2022 or earlier, that portion continues to accrue at the higher rate while any 2023-and-later balance uses the lower one.
If You Have a Mortgage Escrow
If your mortgage includes an escrow account, your lender is responsible for pulling your bill and paying it on time. Cook County doesn’t bill mortgage companies directly; lenders use an online mass-payment system to look up and pay taxes on properties they service.9Cook County Treasurer’s Office. Mortgage Company Payments A delayed second installment doesn’t change that responsibility, but it can create problems. When a bill arrives four or five months late, the sudden escrow disbursement can create a shortage and push up your monthly mortgage payment the following year.
Loans also get sold, escrow accounts get miscalculated, and bills occasionally slip through the cracks. After each installment period, check the online portal to confirm that your lender actually paid. If they didn’t, the delinquent balance is still yours.