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Updated 2025 Tax Year

Grundy County
Property Tax Guide

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

9 Official Sources
8 min read
Quick Facts
Tax Rate
1.8% to 3.2% of market value, varies by taxing districts and location within county
1st Due
Jun 1
2nd Due
Sep 1
Exemptions
4+ Available
Section 1

How Property Tax Works

Grundy County, Illinois operates under a property tax system that funds essential local services including schools, municipalities, townships, and county operations. Property taxes are the primary revenue source for these local governments, with the Illinois Property Tax Extension Limitation Law (PTELL) providing some limitations on tax increases. The county follows Illinois' standard assessment practices, with residential properties assessed at 33.33% of fair market value.

Effective tax rates in Grundy County typically range from approximately 1.8% to 3.2% of market value, though actual rates vary significantly by location within the county due to different combinations of special taxing districts. Each property's total tax rate depends on which school district, municipality, township, park district, fire protection district, and other local taxing bodies serve that specific location. The Illinois statewide average effective rate is approximately 2.27%, and Grundy County rates generally fall within this range depending on the local taxing districts.

Section 2

What Makes Up Your Tax Bill

The 2025 Grundy County property tax rates have not yet been finalized, as they will be determined by governing authorities in the coming months. Property owners should check the county's official website for updates when the 2025 rates become available.

ComponentApproximate Rate RangeDescription
County General0.3% - 0.5%County operations, services, and infrastructure
School Districts3.0% - 5.5%Elementary and high school district levies (varies by district)
Township0.1% - 0.3%Township services and road maintenance
Municipality0.2% - 0.8%City/village services (incorporated areas only)
Fire Protection0.1% - 0.4%Fire district services (varies by district)
Park Districts0.1% - 0.3%Parks and recreation (where applicable)
Other Special Districts0.0% - 0.5%Library, sanitary, drainage districts as applicable

Note: Rates shown are estimates for the 2024 tax year payable in 2025. Actual rates vary by specific location and combination of taxing districts.

Section 3

When Are Property Taxes Due?

For the 2025/2026 tax year in Grundy 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 Grundy County are additional property tax assessments that occur when there are changes to a property's assessed value outside the regular assessment cycle. Common triggers include new construction, substantial improvements, additions, or corrections to the original assessment. These supplemental bills are calculated by applying the current tax rate to the difference between the new assessed value and the previously assessed value.

For example, if a property owner completes a $50,000 addition that increases the assessed value by $16,650 (at 33.33% assessment ratio), and the total tax rate is 7.5%, the supplemental tax would be approximately $1,249 ($16,650 × 0.075). Supplemental taxes are typically prorated based on the portion of the tax year remaining when the improvement was completed and become part of the ongoing annual tax obligation.

Example Calculation

Example 1: $300,000 Home

  • Market Value: $300,000
  • Assessed Value (33.33%): $100,000
  • Less Homeowner Exemption: -$10,000 (application required)
  • Net Taxable Value: $90,000
  • Annual Tax (at 7.0% rate): $6,300
  • Monthly Escrow: $525

Example 2: $600,000 Home

  • Market Value: $600,000
  • Assessed Value (33.33%): $200,000
  • Less Homeowner Exemption: -$10,000 (application required)
  • Net Taxable Value: $190,000
  • Annual Tax (at 7.5% rate): $14,250
  • Monthly Escrow: $1,188

Example 3: $1,000,000 Home

  • Market Value: $1,000,000
  • Assessed Value (33.33%): $333,300
  • Less Homeowner Exemption: -$10,000 (application required)
  • Net Taxable Value: $323,300
  • Annual Tax (at 8.0% rate): $25,864
  • Monthly Escrow: $2,155

Note: Tax rates vary by location within the county. Exemptions require annual application and are not automatically applied.

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Section 5

Escrow & Property Taxes

Most mortgage lenders in Grundy County require property tax escrow accounts for borrowers with less than 20% down payment, though some may require it regardless of down payment amount. Lenders collect approximately 1/12 of the estimated annual property tax amount with each monthly mortgage payment, depositing these funds into an escrow account. When property tax bills are due (typically June 13th for the first installment and September 5th for the second installment), the lender pays the taxes directly to the county on behalf of the homeowner.

Property owners with escrowed taxes should verify that their lender receives and pays tax bills on time, as the homeowner remains ultimately responsible for timely payment even when using escrow. Lenders typically conduct annual escrow analyses to adjust monthly payment amounts based on actual tax bills and account balances. If property taxes increase significantly due to reassessment or rate changes, lenders may require additional escrow payments or increase monthly amounts to ensure adequate funds are available for future tax payments.

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 Grundy County property taxes due for 2025? A: The first installment is due June 13, 2025, and the second installment is due September 5, 2025. Tax bills are mailed no later than May 13th.

Q: What homeowner tax credits are available and how do I apply? A: The Homeowner Exemption reduces equalized assessed value by up to $10,000 and requires application. Additional exemptions include Disabled Veterans' exemptions (up to $6,000 reduction in EAV) and Senior Citizens exemptions. All exemptions require separate applications and are not automatic.

Q: How does the Homestead exemption work? A: The Homestead exemption (Homeowner Exemption) reduces your property's equalized assessed value by up to $10,000, which typically saves $700-$800 annually depending on your tax rate. You must own and occupy the property and file an application with the county assessor.

Q: When do I need to apply for exemptions? A: The filing deadline for most exemptions, including the Homeowner Exemption, is December 31st of each year. For disabled veterans' exemptions, you must have owned and occupied the property for two years before applying.

Q: How often are properties reassessed in Grundy County? A: Illinois law requires reassessment at least every four years, though some counties reassess more frequently. Contact the Grundy County Assessor's office for the specific reassessment schedule and appeal deadlines.

Q: What are the penalties for late property tax payments? A: Late payments typically incur interest charges and penalties. Contact the Grundy County Treasurer's office for current penalty rates and payment options for delinquent taxes.

Q: Can I pay my property taxes online? A: Many Illinois counties offer online payment options. Check the Grundy County Treasurer's website for available electronic payment methods and any associated convenience fees.

Q: Why do property tax rates vary within Grundy County? A: Tax rates depend on which combination of local taxing districts serve your property, including school districts, municipalities, townships, fire districts, park districts, and other special districts. Each district sets its own levy, creating different total rates across the county.

Q: What is the Property Tax Extension Limitation Law (PTELL)? A: PTELL limits the annual increase in property tax extensions for most taxing districts to 5% or the rate of inflation, whichever is less. This helps control property tax growth, though new construction and voter-approved increases can exceed these limits.

Q: How do I appeal my property assessment? A: Property assessment appeals must be filed with the Grundy County Board of Review within specific deadlines, typically 30 days after assessment notices are mailed. Contact the County Assessor's office for appeal procedures and required documentation.

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