Property tax due dates under Illinois law
Property tax due dates in Illinois come from one state law, which sets two installment deadlines. A first installment still unpaid on June 1 is delinquent and bears interest after that date [1]. When the tax bill prints a later due date, the installment is delinquent only if still unpaid the day after that date [1]. The second installment works the same way with September 1 [1].
In a county with fewer than 3 million people, the interest on a late installment is 1.5% a month or part of a month [1]. The same law lets such a county pass an ordinance that makes half of each installment due 60 days later [1].
County dates: Will and Grundy in 2026
County dates are printed on each county's bill and calendar. For 2025 taxes, paid in 2026, Will County's installments were due June 1 and September 1 [2]. Grundy County's were due Friday, June 26 and Friday, September 4 [4]. Grundy County's dates fall after June 1 and September 1, which state law allows when the tax bill prints a later due date [1][4].
2025 taxes, paid in 2026 | Will County | Grundy County |
|---|---|---|
Bills mailed | May 1, 2026 | No later than May 22, 2026 |
First installment due | June 1, 2026 | June 26, 2026 |
Second installment due | September 1, 2026 | September 4, 2026 |
Late installment | 1.5% interest a month | 1.5% a month |
Unpaid taxes | $10 publication fee collected from October 7, 2026 | $10 publication fee added after October 1, 2026 |
Every figure in the table is from the Will County Treasurer's 2026 tax calendar and the Grundy County Treasurer's page [2][4].
First tax bill: the year you buy
The first tax bill after you buy can cover months when the seller still owned the home. The Will County Treasurer's FAQ says real estate taxes are "billed a year in arrear" [3]. The office mails each bill to the owner of record at the time the bills are printed [3].
For the seller's share, the same FAQ says to check your closing documents for a credit for taxes issued at the closing [3]. Further questions go to your attorney or closing agent, it says [3]. If your deed was recorded after May 1, Will County mails tax bills to new owners beginning in June [3].
For example, a buyer who closes on a Will County home in November 2026 is billed for 2026 taxes in 2027, because the taxes are billed a year behind [3]. Your own homestead exemption, which can lower that bill, is covered in where to apply for a homestead exemption in Illinois.
Escrow accounts: when your lender pays
Escrow is money your mortgage lender holds to pay bills like property taxes for you. In Will County, mortgage companies that pay taxes through escrow request and receive the tax bills electronically, and the owner still gets a bill for their records [3].
Illinois law protects you if the lender is the one who pays late. When taxes go delinquent through the lender's fault, the interest is charged to the lender, not to you [1]. The lender must also pay the taxes and remove any lien, a legal claim against the home, that the delinquency caused [1]. That applies when you made every payment due under the mortgage, the lender held escrow funds for the taxes, and those funds were enough [1].
Tax lookup: a home's bill before you buy
Tax lookups on both county sites let you see a home's tax information before you make an offer. Will County's tax lookup asks for the 14 or 16 digit Property Index Number, or PIN, printed on the tax bill [3][5]. The lookup page also links to help for finding a PIN [5]. Grundy County's Property Tax Inquiry Portal shows parcel information, payment history and current amounts due [4].
How to check a home's property taxes before and after you buy
- Find the home's PIN Get the Property Index Number from the tax bill or the county's lookup page.
- Read the last bill Look up the home's most recent tax bill and payment history on the county site.
- Check your closing papers Look for a credit for taxes at the closing, as the Will County Treasurer advises.
- Put both due dates on your calendar Use the two installment dates printed on your county's tax bill.
- Keep your copy if your lender pays With an escrow account, keep the bill the county mails you for your records.
What it means if you buy in Illinois
If you are buying in Illinois, the property tax bill is part of what the home costs each year, and both counties let you look it up by parcel [4][5]. Read the last bill before you make an offer, and check your closing papers for a credit for taxes [3]. Once the home is yours, put your county's two due dates on your calendar [2][4].
Still shopping for the right home? The two steps below are where to start.
