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Updated 2025 Tax Year

Mercer County
Property Tax Guide

Everything you need to know about property taxes in Mercer County, IL. Rates, due dates, exemptions, and how it affects your monthly payment.

10 Official Sources
8 min read
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Quick Facts
Tax Rate
2.225% base county rate, varies by district with overlapping taxing bodies
1st Due
Jun 1
2nd Due
Sep 1
Exemptions
5+ Available
Section 1

How Property Tax Works

Mercer County, Illinois operates under a property tax system that funds essential local services including schools, county government, townships, and special districts. Property taxes are assessed annually based on the equalized assessed value (EAV) of real estate, which is typically one-third of fair market value. The county follows Illinois state law requiring assessments to be conducted every four years, with interim updates for new construction and ownership changes.

The effective property tax rate in Mercer County varies significantly by location within the county due to overlapping taxing districts including school districts, municipalities, fire protection districts, and library districts. The base county rate is fixed at 22.25 mills (2.225%), but total rates typically range from approximately 6% to 10% when all local taxing districts are combined. Property owners receive tax bills twice yearly, with payments due June 30th and September 30th for the current tax year cycle ending in 2026.

Section 2

What Makes Up Your Tax Bill

ComponentRate (Mills)Description
Mercer County General22.25Fixed rate for general county operations and services
School DistrictsVariesElementary and high school districts (rates vary by district)
TownshipVariesTownship government services and road maintenance
MunicipalityVariesCity/village services (if applicable to property location)
Fire ProtectionVariesFire department services (rural areas)
Library DistrictVariesPublic library services (where applicable)
Special DistrictsVariesDrainage, park, or other special purpose districts

Note: These rates apply to the FY 2025-2026 levy year. Total effective rates vary significantly by specific location within Mercer County due to different combinations of taxing districts. Contact the Mercer County Clerk's office for your property's specific tax code and applicable districts.

Section 3

When Are Property Taxes Due?

For the 2025/2026 tax year in Mercer County, property taxes are due in two installments:

First Installment
Jun 1
Delinquent after Dec 10
Second Installment
Sep 1
Delinquent after Apr 10
Pro tip: If you pay through mortgage escrow, your lender splits these payments across your monthly mortgage. If you pay directly, set calendar reminders to avoid late penalties.
Section 4

Supplemental Tax Bills

Supplemental taxes in Mercer County are triggered primarily by new construction, major improvements, or changes in property ownership that result in reassessment. When property improvements are completed or ownership transfers occur, the county assessor reviews the property and may adjust the assessed value to reflect current market conditions. Illinois law requires that any increase in assessed value be applied proportionally throughout the tax year.

Supplemental taxes are calculated by taking the difference between the new assessed value and the original assessed value, then applying the current tax rate to that difference. For example, if a property's assessed value increases from $100,000 to $120,000 due to new construction, the supplemental tax would be calculated on the $20,000 difference multiplied by the applicable tax rate. Mercer County has been issued an equalization factor of 1.0000, meaning no additional state-level adjustments are applied to local assessments.

Example Calculation

Example 1: $300,000 Home

  • Market Value: $300,000
  • Assessed Value (33.33%): $100,000
  • Less Homeowner Exemption: $10,000 (if applied for)
  • Net Taxable Value: $90,000
  • Annual Tax (8% effective rate): $7,200
  • Monthly Escrow: $600

Example 2: $600,000 Home

  • Market Value: $600,000
  • Assessed Value (33.33%): $200,000
  • Less Homeowner Exemption: $10,000 (if applied for)
  • Net Taxable Value: $190,000
  • Annual Tax (8% effective rate): $15,200
  • Monthly Escrow: $1,267

Example 3: $1,000,000 Home

  • Market Value: $1,000,000
  • Assessed Value (33.33%): $333,333
  • Less Homeowner Exemption: $10,000 (if applied for)
  • Net Taxable Value: $323,333
  • Annual Tax (8% effective rate): $25,867
  • Monthly Escrow: $2,156

Note: Homeowner exemption requires annual application and is not automatic. Actual tax rates vary by specific taxing districts applicable to each property location.

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Section 5

Escrow & Property Taxes

Most mortgage lenders in Mercer County require property tax escrow accounts for borrowers with less than 20% down payment or upon borrower request. Lenders collect monthly payments equal to 1/12th of the annual property tax bill plus insurance premiums. The lender is responsible for making timely payments to the county collector on the borrower's behalf, typically paying both installments (June 30th and September 30th) from the escrow account.

Property owners should verify that their lender has current tax information, especially after reassessments or changes in exemption status. Lenders may adjust monthly escrow payments annually based on actual tax bills and account balances. If escrow accounts have insufficient funds, lenders may require additional payments or increase monthly collections. Property owners remain ultimately responsible for ensuring taxes are paid timely, even when using escrow services, and should monitor their annual escrow analysis statements for accuracy.

How HonestCasa Helps
  • Understand whether your escrow is set correctly
  • See how rising taxes will change your monthly payment
  • Plan ahead instead of being surprised by "shortage" letters
Section 6

Frequently Asked Questions

Q: When are property taxes due in Mercer County? A: For the current tax cycle, the first installment is due June 30, 2026, and the second installment is due September 30, 2026. Late payments incur penalties and interest charges.

Q: What is the homeowner exemption and how do I apply? A: The homeowner exemption reduces your property's equalized assessed value by up to $10,000 for owner-occupied residences. This is NOT automatic and requires annual application to the township assessor's office. Application deadlines vary by township but are typically in early spring.

Q: Are there additional tax credits available for seniors or veterans? A: Yes, Illinois offers various tax relief programs including senior citizen homestead exemptions and veterans' disability exemptions. These require separate applications with specific eligibility requirements and documentation. Contact the Mercer County Supervisor of Assessments for current programs and deadlines.

Q: How often are properties reassessed in Mercer County? A: Properties are reassessed every four years as part of the countywide assessment cycle. However, new construction, major improvements, or ownership changes may trigger interim reassessments.

Q: Can I appeal my property assessment? A: Yes, property owners can appeal assessments first to the local Board of Review, then to the Illinois Property Tax Appeal Board (PTAB). Appeals must be filed within specific timeframes following assessment notices.

Q: What penalties apply for late tax payments? A: Late payments incur monthly penalties of 1.5% per month plus interest charges. Properties with delinquent taxes may eventually be subject to tax sale proceedings.

Q: Can I pay property taxes online? A: Contact the Mercer County Collector's office for current online payment options and accepted payment methods. Many Illinois counties offer online payment systems for property taxes.

Q: How do special taxing districts affect my tax bill? A: Your total tax rate includes all applicable taxing districts for your property location, including school districts, fire protection districts, library districts, and others. The specific combination varies by location within Mercer County, which is why tax rates differ significantly between properties.

Verified Sources

Backed by 10 Official Government Sources

Every fact in this guide is sourced from official county, state, and federal documents.

01
County
meeting of the mercer county board of commissionersmercercountypa.gov
02
County
FINAL Tax Computation Report - Fulton Countyfultoncountyil.gov
03
Press Releases Archive - Illinois Department of Revenuetax.illinois.gov
04
County
ILLINOIS COUNTY CLERKS' OFFICIAL PROPERTY TAX ...clerk.kanecountyil.gov
05
County
Home - County Auditor, Mercer County, Ohioauditor.mercercountyohio.gov
06
Tax Doc
Practical Guide to Illinois Property Taxesjeffersoncounty.illinois.gov
07
Tax Doc
Property Tax Relief Information for Veterans and Persons with ...tax.illinois.gov
08
County
Mercer - County Replacement Tax Detail - Illinois.govtax.illinois.gov
09
PT 98-77 - Charitable Ownership/Usetax.illinois.gov
10
March 2020illinois.gov
All sources verified as of 2025 Tax Year

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