"Buying a Home in Illinois: When Are the Two Property Tax Installments Due, and Why Is Cook County's First One Set From Last Year's Bill?"

Early in the year, a property tax bill arrives at your new Cook County home with the word estimate on it. The amount was worked out from a year when the seller still owned the home, with the seller's exemptions left off, and it can look nothing like the tax figure on your Closing Disclosure. The bill that settles the actual tax comes months later, and that is the one your escrow account has to be ready for.

Illinois bills a year's property tax the following year, in two installments. In most counties the first is due June 1 and the second September 1, or later if the bill prints a later date. In Cook County, the first installment is an estimate, 55 percent of last year's bill, and the second installment is the difference between that estimate and the year's actual tax.

I'm Jeff Moran, a mortgage broker in Bluffton, South Carolina, originating since 1996, NMLS #483943, through C2 Financial Corporation, licensed in fifteen states, including Illinois. An Illinois purchase puts the tax calendar in the middle of three numbers you care about: the seller's credit at closing, your escrow deposit, and the monthly payment you live with afterward.

When are property taxes due in Illinois?

The Cook County Treasurer's taxpayer pamphlet notes that Cook County property taxes are collected in arrears. In plain terms, the bills mailed in a given year cover the tax year before it. So the bills that reach you in 2027 are for tax year 2026, including the months before your closing when the seller owned the home.

Under Section 21-15 of the Illinois Property Tax Code, the first installment of unpaid tax becomes delinquent after June 1, or after the due date printed on the bill if that date is later. The second installment becomes delinquent after September 1, or after its own printed due date if later, and interest runs from that point. The Illinois Department of Revenue's answer on when property tax has to be paid puts it in fewer words: in most counties the tax is paid in two installments, usually June 1 and September 1. If the bill in front of you prints a later date, that later date is the one that counts.

How does accelerated billing work in Cook County?

Cook County runs on a different schedule, written in the statute for any county with 3,000,000 or more residents. Under Section 21-30 of the Property Tax Code, the county mails an estimated bill for the first installment by January 31. That first installment is computed at 55 percent of the total of last year's bill for the same property. By June 30 the county prepares the actual bills, which show the total tax for the year, the estimate already billed, and the balance owed as the second installment.

That first installment is 55 percent of a bill from a year when the seller owned the home, so it was never meant to be half of your tax. The Cook County Assessor's office explains that first installment bills do not reflect homeowner, senior or other exemptions. Those show up on the second installment bill. Everything that changed since last year lands on that second bill: a reassessment, an exemption that ended with the seller, one you filed for in your own name, and the new tax rates.

The statute also sets default dates for Cook County, and they are earlier than the rest of the state. Section 21-25 makes the estimated first installment delinquent after March 1 in a county of this size, and the second installment delinquent after August 1. In practice, the Treasurer has published later dates in recent years.

The Cook County dates change from year to year, and the date the Treasurer publishes is the one that counts. For tax year 2025, the Cook County Treasurer's due dates page lists the first installment due Wednesday, April 1, 2026 and the second installment due Thursday, October 1, 2026. The April date was an exception. The Treasurer's office explains that the prior year's second installment was not due until December 15, 2025, so this first installment moved from its usual March 1 to April 1. Please take the dates for your own bill from the bill itself or from the Treasurer's site.

Smaller counties can choose this method too. Section 21-20 lets a county under 3,000,000 residents adopt accelerated billing by ordinance or resolution, with the estimated first installment delinquent after a date the county sets, no later than June 1, and the second after August 1.

Your first year of Illinois tax bills after closing

Say you close on a Cook County home in the second half of 2026. The tax year 2025 bills were due April 1 and October 1 of 2026, and they cover a year you did not own the home, so they are the seller's to pay. Your attorney and the title company handle any installment still open at closing.

Tax year 2026 is the year you and the seller share, and its bills come in 2027. The first installment arrives early in 2027 at 55 percent of the seller's 2025 total, exemptions left off. The second installment arrives later in 2027 with the actual 2026 tax on it, including a reassessment if the township had one. If you applied for the homeowner exemption in your own name, that is where you will see it, and I go through the filing timeline in whether the seller's Illinois homeowner exemption carries over to you. A newly built home runs on a different clock, because the land may have been taxed as a vacant lot, and how the first property tax bill works on new construction covers that case.

The seller's tax credit at closing, and your cash to close

Because the 2026 tax is billed in 2027, the seller's months of 2026 are unpaid on closing day. Illinois contracts usually handle that with a credit from the seller to you on the settlement statement, figured from the most recent full-year tax bill and prorated to the closing date.

Your contract sets what percentage of that bill the credit is figured on, and it can be set above 100 percent. The reason is that the most recent bill may not predict the next one: the assessment can change, an exemption can disappear, and the rates can go up.

That credit lowers your cash to close. Once the 2027 bills arrive, you pay the whole year, and the seller's share was already handed to you at the table. The credit settles the seller's own share of the tax rather than paying your costs. That is why, as I explain in whether the prorated tax credit counts against the seller concession limit, it does not use up the Fannie Mae and Freddie Mac ceiling on seller contributions.

Setting up your escrow account, and when it catches up to the actual tax

An escrow account collects a twelfth of the expected annual tax and insurance with each mortgage payment, and the servicer pays the bills when they come due. The mechanics are in how escrow accounts work. The federal rule behind the account, Regulation X at 12 CFR 1024.17, lets the servicer keep a cushion of up to one-sixth of what the account is expected to pay out over the year.

If your escrow was set up from the seller's last bill, the monthly deposit is sized to last year's tax. The first installment the servicer pays is 55 percent of that same bill, so the account looks healthy in the spring. The second installment carries the actual tax, with the reassessment and the exemption change in it, and if the actual tax is higher than last year's, the account comes up short right there.

Under Regulation X the servicer runs an escrow analysis at least once a year, and a shortage of one month's escrow payment or more can be spread over at least twelve months rather than demanded at once. So the account catches up to the higher tax through a changed monthly payment the following year.

On an Illinois purchase I would rather build the tax line from the county's own figures for the address than from the seller's last bill alone. That means the current assessed value, the current rate, and whether the exemption on the seller's bill will still be there once the home is in your name. Years later, once on-time payments bring your loan down far enough, Illinois gives you a choice about keeping the account at all, which I cover in whether you can close your Illinois escrow account at 65 percent.

Three things that trip up a first Illinois tax year

Reading the first installment as half the year. It is 55 percent of last year's bill, and last year's bill was the seller's. If the tax rose, the second installment will be larger than the first, by design.

Counting on the seller's exemption. The homeowner exemption on the seller's bill belonged to the seller, and it appears in your name only after you apply. An escrow account sized to a bill that still carries the seller's exemption is sized a little low.

Planning from another state's calendar. A Kansas county mails one statement in November with both halves on it, which I describe in when Kansas property taxes are due after a fall closing. In Illinois you plan for two separate bills months apart, with the change for the year arriving on the second one.

An example, with made-up numbers

Numbers below are invented to show the mechanism. Say you close on a Cook County home on August 15, 2026, and the seller's tax year 2025 bill totaled 9,000 dollars. Your contract sets the proration at 110 percent of that bill, and the seller owned the home for the first 227 days of 2026.

Seller's 2025 bill (invented)                    $9,000
Proration basis at 110%                          $9,900
Seller's 227 days of 2026 (227/365)              $6,157
                                                 ------
Credit to you at closing                         $6,157

Your escrow account is set up from the same 9,000 dollar bill, so the monthly tax deposit is 750 dollars. The tax year 2026 bills arrive in 2027.

First installment, 2027 (55% of $9,000)          $4,950
Actual 2026 tax after reassessment (invented)   $10,200
                                                 ------
Second installment (actual minus estimate)       $5,250

The servicer paid 10,200 dollars in all against the 9,000 dollars the account collected, so the escrow analysis finds a 1,200 dollar shortage.

New monthly tax deposit ($10,200 / 12)             $850
Shortage spread over 12 months ($1,200 / 12)       $100
                                                 ------
Monthly tax escrow for the next year               $950

Your tax line moves from 750 dollars to 950 dollars a month for a year, then settles at 850 dollars once the shortage is repaid. The proration above 100 percent kept the seller's credit close to their share of the actual bill.

Planning your Illinois purchase around the two installments

An Illinois pre-approval is where I review your income, debts and credit with your documents in hand and price the tax, the transfer taxes and the attorney's fee for the actual municipality. The Illinois mortgage page covers the rest of an Illinois closing, including the two-attorney model.

Run your numbers and you will see rates for your scenario, your debt ratio and closing costs priced for Illinois. If you would rather talk it through, you are welcome to call me, and we can go over how the two installments fit with your first year in the home.

Nothing here is a loan approval, a denial, a commitment to lend, or tax or legal advice. The county treasurer bills and collects the tax, your attorney negotiates the proration, and your closing papers show how the year was handled.

Common questions

When are property taxes due in Illinois?

In most Illinois counties a year's property tax is billed the following year in two installments. Under Section 21-15 of the Property Tax Code the first becomes delinquent after June 1 and the second after September 1, or after a later date printed on the bill. Cook County runs earlier, with an estimated first installment early in the year.

When are Cook County property taxes due?

The statute sets a March 1 default for Cook County's estimated first installment, and an August 1 default for the second installment. The actual dates move from year to year: for tax year 2025, the Cook County Treasurer listed the first installment due April 1, 2026 and the second due October 1, 2026. The bill itself carries the dates for your year.

Why is my first Cook County property tax bill only 55 percent of last year's?

Cook County uses accelerated billing under Section 21-30 of the Illinois Property Tax Code. The first installment is an estimate computed at 55 percent of the total of the prior year's bill for the same property, mailed by January 31, with no exemptions applied. The actual bill is prepared by June 30 and shows the total tax for the year, the estimate already billed, and the balance owed as the second installment.

What happens to my escrow account when the second installment is higher than the estimate?

If the actual tax for the year ran above the figure the account was built on, the account comes up short when the servicer pays the second installment. Under Regulation X the servicer runs an escrow analysis at least once a year, and a shortage of one month's escrow payment or more can be spread over at least twelve months rather than collected at once. Your monthly payment usually rises for the next year to cover the higher tax and the repayment.

Do I get a property tax credit from the seller at an Illinois closing?

Yes, in the ordinary Illinois contract. The tax for the year of your closing is billed the following year, so the seller's months are unpaid on closing day. The contract prorates the tax to the closing date based on a percentage of the most recent full-year bill. The credit lowers your cash to close, and because it settles the seller's own share rather than paying your costs, it does not count against the Fannie Mae or Freddie Mac limit on seller contributions.