Property tax in Williamson County, Illinois
In Williamson County, the property tax bill comes from the Williamson County Treasurer. The 2025 Payable 2026 bill is paid in 2 installments, and the next one is due October 16, 2026. You can look up and pay the bill on the county's own payment page. Taken from Williamson County's own pages, checked September 23, 2026.
The median property tax bill in Williamson County, Illinois is $2,690 a year, which is about 1.72% of the county's median home value of $156,400. That effective rate is lower than the typical Illinois county (1.81%) and higher than the national median (0.81%). These are American Community Survey 5-year estimates (2024); your own bill depends on your home's assessed value and any exemptions.
Who sends the property tax bill in Williamson County, and how do you pay it?
The bill comes from the Williamson County Treasurer. The value it is based on is set by a separate office, the Williamson County Supervisor of Assessments, which is who to ask if the value looks wrong. For how to look up and pay the bill, go to the county's own payment information.
The Supervisor of Assessments' office handles assessments, and an owner can ask that office to review a value before filing a complaint with the Board of Review; the Treasurer only collects the tax. One county bill carries the taxes of every local district the property sits in, including schools, cities, park districts and airport districts. You can pay by mail, in person, at the night drop box, at most local banks before the due date, or online and by phone, where a convenience fee applies to card payments. Mobile home taxes are paid through a separate online link on the Treasurer's page. The Treasurer runs a prepayment program (cash or check, $20 minimum) for paying next year's bill ahead. A Board of Review decision can be appealed to the Illinois Property Tax Appeal Board.
When are property taxes due in Williamson County?
For the 2025 Payable 2026 bill, Williamson County splits the bill into 2 payments, the first due October 16, 2026 and the last November 16, 2026. An installment not paid by its due date is charged interest of 1.5% a month, or any part of a month, starting the day after the due date, as Illinois law requires. A $10 fee per parcel is added when delinquent notices are sent by certified mail. Taxes still unpaid after the second installment due date are published as delinquent and sold at the county's annual tax sale; the county sells the unpaid tax, not the home, and the owner then pays back the buyer through the County Clerk, with the cost rising the longer it takes.
| Payment | Due | Note |
|---|---|---|
| First installment | October 16, 2026 | Bills were mailed August 14, 2026. A mailed payment counts as on time only with an official U.S. postmark dated on or before the due date. |
| Second installment | November 16, 2026 | After this date, payments must be made at the Treasurer's office. |
From Williamson County's published schedule, checked September 23, 2026. If a date falls on a weekend or holiday, the county's own rules on the next business day apply.
Estimate the property tax on a home in Williamson County
Enter a home's market value for a ballpark at Williamson County's average effective rate of 1.72% (Census). The real bill depends on the home's assessed value, the millage where it sits and any exemptions.
Estimated property tax: $2,690 / year
Property tax in Williamson County at a glance
| Measure | Value |
|---|---|
| Median annual property tax | $2,690 |
| Median home value | $156,400 |
| Effective tax rate | 1.72% |
| Typical Illinois county rate | 1.81% |
| National median county rate | 0.81% |
Effective rate = median real estate taxes paid divided by median home value. Source: U.S. Census Bureau, American Community Survey 5-year estimates.
How does Williamson County compare in Illinois?
Among Illinois's 102 counties, Williamson County has the 61st highest effective property-tax rate: 60 rank higher and 41 rank lower. That is near the middle for Illinois. Nationally, it ranks 180th of 3135 US counties by effective rate. See every Illinois county ranked.
How much do homeowners in Williamson County actually pay?
The median is only the middle bill. Across Williamson County's 20,477 owner-occupied homes, 42% pay $3,000 or more a year in property tax, 60% pay at least $2,000, and 11.1% pay under $800. Another 4.7% report paying no property tax at all, which usually means an exemption covers the whole bill.
| Annual bill | Homes | Share |
|---|---|---|
| Under $800 | 2,283 | 11.1% |
| $800 to $1,499 | 2,923 | 14.3% |
| $1,500 to $1,999 | 1,999 | 9.8% |
| $2,000 to $2,999 | 3,696 | 18% |
| $3,000 or more | 8,608 | 42% |
| No property tax paid | 968 | 4.7% |
Owners with a mortgage pay a median of $3,136 and owners without one pay $2,062. Owners who have paid off a home have usually held it longer, and in states that cap how fast an existing owner's assessment can rise, long-held homes carry lower assessed values. Census table B25103.
How does the Williamson County property tax bill compare with local incomes?
The median property tax bill of $2,690 is about 3.3% of the median income of Williamson County homeowner households, $82,096 a year. That compares two middles, so a retiree in a long-held home can pay a far larger share. 70.7% of Williamson County's occupied homes are lived in by their owners; renters pay property tax too, just folded into rent.
Have property taxes gone up in Williamson County?
Yes. The median bill went from $1,827 in 2015-2019 to $2,690 in 2020-2024, a 47.2% rise. Over the same span the median home value moved 36.1%, from $114,900 to $156,400. Bills rose faster than values, which usually means local rates went up or an exemption shrank.
Two Census ACS 5-year periods with no survey years in common, in each period's own dollars. A change counts only if it exceeds the combined 90% margin of error.
Property tax in counties next to Williamson County
Williamson County borders 5 counties.
| County | Effective rate | Median bill | Median home value |
|---|---|---|---|
| Jackson County, IL | 1.84% | $2,526 | $137,300 |
| Williamson County, IL (this county) | 1.72% | $2,690 | $156,400 |
| Saline County, IL | 1.69% | $1,597 | $94,300 |
| Franklin County, IL | 1.57% | $1,394 | $89,000 |
| Union County, IL | 1.3% | $1,712 | $131,700 |
| Johnson County, IL | 1.24% | $1,992 | $160,500 |
How is a home assessed in Williamson County?
Illinois assesses homes at 33.33% of market value in every county, Williamson County included. How Illinois assesses and reappraises homes.
Is there a homestead exemption in Williamson County?
Yes. Illinois's General Homestead Exemption is $6,000 of equalized assessed value in most counties, $8,000 in counties next to Cook, and $10,000 in Cook County. That is the Illinois rule, and it applies in Williamson County. Illinois's exemptions and relief programs in full.
Williamson County does not add relief programs of its own beyond the Illinois ones (checked September 23, 2026).
How to appeal your Williamson County property assessment
In Williamson County you appeal to the Williamson County Board of Review. The deadline: A complaint must be filed within 30 days after the Supervisor of Assessments publishes the assessment list for the year, as Illinois law requires. Complaint forms are available only from the Supervisor of Assessments' office, in person or by mail on request, and faxed or emailed complaints are not accepted. The list for the 2025 assessment, which is billed in 2026, was published in April 2026. How to file. Checked September 23, 2026 against the official appeal rules.
How Illinois's appeal process works, including the next level if the first one turns you down.
Illinois rules from primary state sources, reviewed September 7, 2026; sources on the Illinois page.
Work out your own numbers
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How much house can I afford?
Your income, debts and down payment against the 28/36 rule lenders actually use, with Williamson County's tax rate to hand.
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Mortgage calculator
Monthly payment with principal, interest, tax and insurance, plus what an extra payment saves you.
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Illinois income tax
Brackets, standard deduction and what Illinois actually taxes.
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Sales tax in Williamson County
The other local tax: combined state and local rate for this county.
Sources
- Median real estate taxes paid and median home value for Williamson County, Illinois: U.S. Census Bureau, American Community Survey 5-year estimates (2020-2024), tables B25103, B25077, B25102, B25119 and B25003; the five-year comparison uses the 2015-2019 estimates. Neighboring counties: Census county adjacency file.