Property tax in Mercer County, Illinois
In Mercer County, the property tax bill comes from the Mercer County Treasurer and Collector. Every due date for the 2025 payable 2026 bill has passed, and the county had not posted the next cycle's dates when we checked. You can look up and pay the bill on the county's own payment page. Taken from Mercer County's own pages, checked September 23, 2026.
The median property tax bill in Mercer County, Illinois is $2,878 a year, which is about 1.96% of the county's median home value of $146,700. That effective rate is higher 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 Mercer County, and how do you pay it?
The bill comes from the Mercer County Treasurer and Collector. The value it is based on is set by a separate office, the Mercer County Supervisor of Assessments (Chief County Assessment Officer), with the township assessors, 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.
Township assessors value homes, and the county asks owners to take assessment questions to their township assessor first. Address changes and exemptions are handled by the Supervisor of Assessments, not the Treasurer, and all exemption applications except open space are due December 31. A decision of the Board of Review can be appealed to the Illinois Property Tax Appeal Board within 30 days of the board's written decision. One county bill carries the taxes of every local district, including schools, cities and villages, townships, fire districts and libraries. Online payments carry a third-party handling fee. Taxes can also be paid at any bank in Mercer County, at People's National Bank in Reynolds or CBI Bank and Trust in Buffalo Prairie, by mail, or in the two courthouse drop boxes, always with the payment stubs. The county has no mobile home privilege tax bill.
When are property taxes due in Mercer County?
Every due date for the 2025 payable 2026 bill has passed, and Mercer County had not posted the next cycle's dates when we checked on September 23, 2026. If that bill is still unpaid, the late-payment rules below apply to it. Counties usually repeat the schedule, but confirm the new dates on your next bill. For the 2025 payable 2026 bill, Mercer County splits the bill into 2 payments, the first due June 26, 2026 and the last September 18, 2026. A late installment is charged a penalty of 1.5% starting the day after its due date, with no grace period. The county describes the penalty as growing by 1.5% every 30 days, but state law sets it at 1.5% a month or part of a month, so each new month adds another 1.5%. Delinquent notices go out October 5, 2026; after that, card and e-check payments stop and only a bank cashier's check, money order or cash is accepted. To stay off the published delinquent list, payment must reach the office by 4 p.m. on October 7, 2026. The last day to pay is November 4, 2026, in the office by 4 p.m. Taxes still unpaid go to the annual tax sale on November 6, 2026, at the courthouse in Aledo, and the county's notice for this sale says the county will acquire the tax certificates for all properties on the delinquent list.
| Payment | Due | Note |
|---|---|---|
| First installment | June 26, 2026 (passed) | Bills for the 2025 tax year were mailed May 26, 2026. Mailed payments count as on time by their postmark date. Local banks in the county take payments without penalty until noon on the Saturday after a due date, but not later. |
| Second installment | September 18, 2026 (passed) |
From Mercer 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 Mercer County
Enter a home's market value for a ballpark at Mercer County's average effective rate of 1.96% (Census). The real bill depends on the home's assessed value, the millage where it sits and any exemptions.
Estimated property tax: $2,875 / year
Property tax in Mercer County at a glance
| Measure | Value |
|---|---|
| Median annual property tax | $2,878 |
| Median home value | $146,700 |
| Effective tax rate | 1.96% |
| 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 Mercer County compare in Illinois?
Among Illinois's 102 counties, Mercer County has the 36th highest effective property-tax rate: 35 rank higher and 66 rank lower. That is on the higher side for Illinois. Nationally, it ranks 98th of 3135 US counties by effective rate. See every Illinois county ranked.
How much do homeowners in Mercer County actually pay?
The median is only the middle bill. Across Mercer County's 5,499 owner-occupied homes, 45.1% pay $3,000 or more a year in property tax, 67.1% pay at least $2,000, and 9.7% pay under $800. Another 4.5% report paying no property tax at all, which usually means an exemption covers the whole bill.
| Annual bill | Homes | Share |
|---|---|---|
| Under $800 | 535 | 9.7% |
| $800 to $1,499 | 520 | 9.5% |
| $1,500 to $1,999 | 510 | 9.3% |
| $2,000 to $2,999 | 1,209 | 22% |
| $3,000 or more | 2,478 | 45.1% |
| No property tax paid | 247 | 4.5% |
Owners with a mortgage pay a median of $3,144 and owners without one pay $2,476. 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 Mercer County property tax bill compare with local incomes?
The median property tax bill of $2,878 is about 3.3% of the median income of Mercer County homeowner households, $87,210 a year. That compares two middles, so a retiree in a long-held home can pay a far larger share. 83.8% of Mercer 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 Mercer County?
Yes. The median bill went from $2,298 in 2015-2019 to $2,878 in 2020-2024, a 25.2% rise. Over the same span the median home value moved 36.3%, from $107,600 to $146,700. Bills rose more slowly than values, which is what assessment caps and falling millage rates do: the county is taxing a smaller share of each home's worth.
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 Mercer County
Mercer County borders 7 counties, 2 of them across the state line.
| County | Effective rate | Median bill | Median home value |
|---|---|---|---|
| Rock Island County, IL | 2.28% | $3,425 | $150,400 |
| Henry County, IL | 1.99% | $3,016 | $151,600 |
| Knox County, IL | 1.96% | $2,190 | $111,900 |
| Mercer County, IL (this county) | 1.96% | $2,878 | $146,700 |
| Warren County, IL | 1.81% | $1,903 | $105,000 |
| Henderson County, IL | 1.58% | $1,651 | $104,400 |
| Des Moines County, IA | 1.51% | $2,058 | $136,500 |
| Louisa County, IA | 1.17% | $1,751 | $150,100 |
How is a home assessed in Mercer County?
Illinois assesses homes at 33.33% of market value in every county, Mercer County included. How Illinois assesses and reappraises homes.
Is there a homestead exemption in Mercer 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 Mercer County. Illinois's exemptions and relief programs in full.
Mercer County does not add relief programs of its own beyond the Illinois ones (checked September 23, 2026).
How to appeal your Mercer County property assessment
In Mercer County you appeal to the Mercer County Board of Review. The deadline: Within 30 days after the county publishes your township's assessment changes in the newspaper, filed on the Board of Review's form; a mailed complaint counts as filed on its postmark date. For 2025 assessments the deadline was November 14, 2025 in Preemption, New Boston, Millersburg and North Henderson townships and November 7, 2025 in the other townships with changes. The county had not yet posted publication dates for 2026 assessments. 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 Mercer 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 Mercer County
The other local tax: combined state and local rate for this county.
Sources
- Median real estate taxes paid and median home value for Mercer 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.