HonestCasa logoHonestCasa
All Tax Guides
Updated 2025 Tax Year

Union County
Property Tax Guide

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

10 Official Sources
8 min read
Calculate Your True CostMortgage Calculator
Quick Facts
Tax Rate
1.5% to 2.5% effective rate (varies by school district and municipality)
Exemptions
5+ Available
Section 1

How Property Tax Works

Union County, Ohio's property tax system operates on a mill-based structure that funds essential local services including schools, county operations, libraries, and various special districts. Property taxes are the primary revenue source for these services, with the Ohio Department of Taxation overseeing assessment standards while local officials handle collection and administration. The county uses a 35% assessment ratio on market value, meaning your taxable assessed value is calculated at 35% of your property's appraised market value.

Effective tax rates in Union County vary significantly by location within the county due to different combinations of school districts, municipalities, and special taxing districts. Property owners can expect rates ranging from approximately 1.5% to 2.5% of market value depending on their specific tax district. The 2025 tax year shows an expected increase of 7.5% over the previous year, though exact millage rates vary by district. Property owners should verify their specific rate with the Union County Auditor's office, as rates differ between areas served by different school districts and municipal services.

Section 2

What Makes Up Your Tax Bill

ComponentRate (Mills)Description
Base County Levy~5.5 millsGeneral county operations, sheriff, courts
School Districts~15-25 millsVaries by district (Big Walnut, Marysville, etc.)
Municipal Levies~2-8 millsCity/village services (varies by location)
Library Levy~1-2 millsUnion County library system
Special Assessments~0.5-3 millsFire districts, parks, other special services
Total Range~24-44 millsEquivalent to 2.4-4.4% of assessed value

Note: These rates apply to Levy Year 2025 (collected in 2026). Actual millage varies significantly by taxing district within Union County. The decimal equivalent shown in research data suggests rates around 20-55 mills (.020-.055) depending on location. Contact the Union County Auditor at (937) 645-3006 for your specific district's exact millage.

Section 3

When Are Property Taxes Due?

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

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 Union County are additional tax bills issued when property ownership changes, new construction is completed, or property improvements are made that increase assessed value during the tax year. These taxes cover the difference between what was originally billed and what should have been billed based on the property's new status or value.

Supplemental taxes are calculated by taking the difference in assessed value, multiplying by your district's mill rate, and prorating for the portion of the tax year remaining. For example, if you complete a $100,000 home addition in July, the additional assessed value would be $35,000 (35% assessment ratio). If your total mill rate is 30 mills, the supplemental tax would be $1,050 ($35,000 × 0.030) prorated for half the year, resulting in approximately $525. These bills are typically issued within 60-90 days of the triggering event and have separate due dates from regular property tax bills.

Example Calculation

Example 1: $300,000 Home

  • Market Value: $300,000
  • Assessed Value (35%): $105,000
  • Less: Homestead Credit (if applied): -$9,170 (35% of $26,200)
  • Net Taxable Value: $95,830
  • Annual Tax (25 mills): $2,396
  • Monthly Escrow: $200

Example 2: $600,000 Home

  • Market Value: $600,000
  • Assessed Value (35%): $210,000
  • Less: Homestead Credit (if applied): -$9,170
  • Net Taxable Value: $200,830
  • Annual Tax (30 mills): $6,025
  • Monthly Escrow: $502

Example 3: $1,000,000 Home

  • Market Value: $1,000,000
  • Assessed Value (35%): $350,000
  • Less: Homestead Credit (if applied): -$9,170
  • Net Taxable Value: $340,830
  • Annual Tax (35 mills): $11,929
  • Monthly Escrow: $994

Note: Homestead and other tax credits require annual application and are not automatic. Mill rates vary by taxing district.

See How Taxes Affect Your Payment

Property taxes are just part of your total monthly cost. Get the full picture.

Calculate Now
Section 5

Escrow & Property Taxes

Most mortgage lenders in Union County require property tax escrow accounts to ensure timely payment of property taxes. Lenders collect 1/12 of your estimated annual property tax bill with each monthly mortgage payment, holding these funds in a dedicated escrow account. Since Union County property taxes are due January 1st for the previous tax year, lenders typically pay the full annual bill when due rather than making installment payments.

Your lender will conduct an annual escrow analysis, usually around your loan anniversary date, to determine if your monthly escrow payment needs adjustment based on actual tax bills and any changes in assessed value. If your escrow account has a surplus over $50, federal law requires the lender to refund the excess or offer to apply it to reduce future payments. Property owners should verify their tax payments through the Union County Treasurer's online portal even when using escrow, as lenders occasionally make errors or late payments that can result in penalties being charged to the property owner.

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 Union County property taxes due for 2025? A: Property taxes for the 2025 levy year are due January 1, 2026. Late payments incur penalties and interest charges starting February 1, 2026.

Q: What tax credits are available and do I need to apply? A: The Homestead Credit (limits assessment increases to 10% annually) and Veteran's Homestead Credit ($50,000 exemption vs. standard $26,200) are available but require annual application through the Union County Auditor's office by December 31st preceding the tax year.

Q: How does the Homestead Credit work? A: The Homestead Credit caps annual assessment increases at 10%, not reducing market value but limiting taxable assessed value growth. You must apply annually, and it only applies to your primary residence. It's a credit that reduces your tax bill, not an exemption from market value.

Q: How often are properties reassessed in Union County? A: Ohio requires counties to conduct full reappraisals every six years, with updates every three years. Union County's next full reappraisal is scheduled for tax year 2027.

Q: Can I appeal my property assessment? A: Yes, you can file an appeal with the Union County Board of Revision by March 31st following the tax lien date. Appeals must be filed annually if you disagree with your assessed value.

Q: What are the penalties for late payment? A: Late payments incur penalties starting at 10% for the first month, plus additional interest charges. Properties become delinquent and subject to foreclosure proceedings if taxes remain unpaid.

Q: Can I pay property taxes online? A: Yes, Union County offers online payment through the Treasurer's website. You can also pay in person at the Treasurer's Office at 233 West 6th Street, Marysville, OH 43040.

Q: Why do property tax rates vary within Union County? A: Tax rates vary because different areas are served by different school districts (Big Walnut, Marysville-Union, etc.), municipalities, fire districts, and other special taxing districts. Your specific location determines which combination of levies applies to your property.

Verified Sources

Backed by 10 Official Government Sources

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

01
Tax Doc
Community Education - Property Taxesunioncountyohio.gov
02
County
Union County Tax Ratesunioncountyohio.gov
03
County
NORTH UNION LOCAL SCHOOL DISTRICT UNION COUNTYn-union.k12.oh.us
04
Tax Doc
Property Tax – Real Propertydam.assets.ohio.gov
05
County
Union County, Ohio - Payment Informationunioncountyohio.gov
06
Tax Doc
Homestead Exemption & Property Tax Rollbacksunioncountyohio.gov
07
County
Union County Newsunioncountyohio.gov
08
County
Union County, Ohio - Auditor FAQunioncountyohio.gov
09
County
UNION COUNTY, OHIOunioncountyohio.gov
10
Tax Doc
Property Tax Resource Hub - Ohio Department of Taxationtax.ohio.gov
All sources verified as of 2025 Tax Year

See the Full Picture of Your Home Costs

Property taxes are just one piece of homeownership. HonestCasa helps you understand your total monthly cost and explore safe ways to access your home equity.

Total Monthly Cost

Mortgage + taxes + insurance + HOA

Equity Growth

Track how your equity grows over time

Safe Equity Access

Options for projects or debt payoff

Run Your ScenarioTry Calculator

Free • No credit check • 2-minute estimate