Illinois Property Taxes Paid in Arrears, Explained

October 21, 2026•5 min read

In Illinois, you pay property taxes a year behind. The bill you pay in 2026 is for the time you lived in the house in 2025. This is called paying "in arrears," and it trips people up all the time, especially at closing. Here is how it works in Naperville, Aurora, Oswego, and Plainfield, Illinois, and what it means for your wallet.

What Does "Paid in Arrears" Mean?

Paying in arrears just means paying after the fact. Think of it like your electric bill. You use the power first, and the bill comes later.

Illinois property taxes work the same way. Your 2025 taxes are billed and paid in 2026. Your 2026 taxes will be billed and paid in 2027. You are always paying for last year.

Most counties split the bill into two payments. For the 2025 taxes paid in 2026:

DuPage County: June 1 and September 1, 2026
Kane County: June 1 and September 1, 2026, per the Kane County Treasurer
Will County: June 1 and September 1, 2026, per the Will County Treasurer
Kendall County: two installments as well. Check the Kendall County Treasurer's due dates page each year.

Aurora sits in four counties, so your due dates and your bill depend on exactly where your home is.

Timeline showing Illinois property taxes are paid in arrears for Naperville and Aurora homeowners

Why This Trips Up Sellers at Closing

Sellers are thrown off by this number every single time. They look at their net sheet and say, "But I already paid my taxes!"

Here is the short answer. The taxes you paid this year were for last year. Since you also lived in the home this year, you owe taxes for that time too. But that bill doesn't come out until next year, after you have moved.

Here's an example. Say you close in November 2026. You already paid both 2026 installments, but those covered 2025. At closing, you still owe your share of 2026 taxes for every day you owned the home this year, January 1 right up to closing day. That is roughly ten and a half months of taxes that haven't been billed yet.

So at closing, you give the buyer a credit for the months you owned the home this year. The buyer then pays the full bill when it arrives. It is not a double charge. It is you paying your share of this year, just early.

Some sellers also owe last year's second installment if it was not paid yet. Your attorney sorts all of this out on the closing statement. If you need one, we trust James F. White and Andrew Heap at Kuhn Heap. Tell them Team Elite sent you.

Why This Trips Up Buyers

On the buyer side, that credit is real money in your pocket at closing. But don't spend it. You will need it when the tax bill shows up.

A few other things catch buyers off guard:

Your first bill may not match the old one. The seller may have had exemptions, like the senior exemption, that you won't get. Your first full bill could be higher.
Contracts often prorate at more than 100%. In many Illinois contracts, the credit is based on the last bill plus a cushion, since taxes usually go up.
Escrow takes time to catch up. If your lender collects taxes in your monthly payment, a jump in the bill can raise your payment later. We explained how that works in our guide to what escrow is.

For the bigger picture on how bills get calculated, see our post on understanding property taxes in Illinois. If your bill feels too high, here is how to appeal your property tax assessment.

How We Help Clients Plan for Taxes

At Team Elite Realtors, we look at the tax history on every home before our buyers write an offer, and we walk our sellers through the proration before closing day. No surprises. We're Julia Corkey and Vickie Schoenfeld, and we're with Baird and Warner, which has been rooted in Chicagoland since 1855.

Want a number before you list? Start with a free instant market analysis, or book a consultation. You can read what past clients say in our Google Reviews.

Frequently Asked Questions

Are Illinois property taxes paid in arrears? Yes. Illinois property taxes are paid a year behind. The bill you pay this year covers last year.

Why do I owe property taxes at closing if I already paid this year? What you paid this year was for last year. At closing, you credit the buyer for the months you owned the home this year, since that bill won't come until next year.

When are property taxes due in DuPage, Kane and Will County? For 2025 taxes paid in 2026, all three counties set installments for June 1 and September 1, 2026. Always check your county treasurer for the current year.

Who is a Realtor near me in Aurora or Naperville who can explain my property taxes? We can. We're Julia Corkey and Vickie Schoenfeld with Team Elite Realtors at Baird and Warner. Call 630-286-9777 or visit www.homesbyteamelite.com.

Shopping for a home? Look at the tax history before you fall in love. Start your search on Zenlist and we will help you read the numbers.

Ready to make your next move in the western suburbs of Chicago?

We are here to help you every step of the way, whether you are buying, selling, or just exploring your options.

Julia Corkey & Vickie Schoenfeld Team Elite Realtors at Baird & Warner

📞 630-286-9777 | 📧 [email protected] | 🌐 www.homesbyteamelite.com

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