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Updated 2025 Tax Year

Rock County
Property Tax Guide

Everything you need to know about property taxes in Rock County, WI. 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
Base rate $3.94 per $1,000 assessed value, total effective rates 1.5-2.5% depending on taxing districts
Exemptions
5+ Available
Section 1

How Property Tax Works

Rock County, Wisconsin operates under the state's property tax system to fund essential local services including schools, county government operations, municipal services, and special districts. Property taxes are the primary revenue source for these public services, with the county collecting taxes on behalf of all taxing jurisdictions within its boundaries.

The effective property tax rate in Rock County varies significantly by location due to different combinations of taxing districts. While the county's base rate is $3.94 per $1,000 of assessed value for the 2025 levy year, property owners may pay additional amounts for school districts, municipalities, technical colleges, and special purpose districts. Total effective rates typically range from 1.5% to 2.5% of assessed value depending on your specific location within Rock County.

Property assessments in Wisconsin are conducted by local assessors and must reflect fair market value as of January 1st each year. Unlike some states, Wisconsin does not impose a statewide assessment cap, meaning assessed values can increase to match market conditions without limitation.

Section 2

What Makes Up Your Tax Bill

ComponentRate per $1,000Description
Rock County$3.94County services, sheriff, courts, health services
School Districts$8.00-$12.00K-12 education (varies by district)
Municipalities$2.00-$6.00City/town services, fire, police
Technical College$0.50-$1.00Blackhawk Technical College district
Special Districts$0.25-$2.00Library, sanitary, fire protection districts

Total Estimated Range: $14.69-$24.94 per $1,000 of assessed value

Rates shown are for the 2025 levy year (taxes due in 2026). Actual rates vary significantly based on your property's location and which taxing districts serve your area. Contact the Rock County Treasurer's office for your specific rate combination.

Section 3

When Are Property Taxes Due?

For the 2025/2026 tax year in Rock 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 Rock County are additional property tax bills issued when property undergoes significant changes after the annual assessment. Common triggers include new construction completion, major improvements like additions or remodels, or changes in property use classification.

Supplemental taxes are calculated by applying the current tax rate to the difference between the old and new assessed values, prorated for the portion of the tax year remaining. For example, if you complete a $100,000 home addition in July and your total tax rate is $20 per $1,000, you would owe approximately $1,000 ($100,000 ÷ 1,000 × $20 × 6/12 months remaining).

These supplemental bills are typically issued 30-90 days after the assessor determines the new value and are due within 30 days of the issue date. Property owners should budget for potential supplemental taxes when planning major improvements during the tax year.

Example Calculation

Example 1: $300,000 Home

  • Assessed Value: $300,000
  • Less: Homestead Credit (if eligible): -$1,200
  • Net Tax Calculation: $300,000 × 0.020 = $6,000
  • Annual Property Tax: $6,000
  • Monthly Escrow: $500

Example 2: $600,000 Home

  • Assessed Value: $600,000
  • Less: Homestead Credit (if eligible): -$800
  • Net Tax Calculation: $600,000 × 0.020 = $12,000
  • Less applicable credit: $11,200
  • Annual Property Tax: $11,200
  • Monthly Escrow: $933

Example 3: $1,000,000 Home

  • Assessed Value: $1,000,000
  • Less: Homestead Credit (if eligible): -$400
  • Net Tax Calculation: $1,000,000 × 0.020 = $20,000
  • Less applicable credit: $19,600
  • Annual Property Tax: $19,600
  • Monthly Escrow: $1,633

Examples use an estimated 2.0% effective rate. Homestead credits shown require application and eligibility varies by income. Actual rates and credits vary by location and individual circumstances.

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Section 5

Escrow & Property Taxes

Most mortgage lenders in Rock County require property tax escrow accounts for loans with less than 20% down payment. Your lender collects 1/12th of your estimated annual property tax bill with each monthly mortgage payment, depositing these funds into an escrow account.

Rock County property taxes are due in two installments: the first by January 31st and the second later in the year. Your lender will pay these bills directly from your escrow account when due. Lenders typically conduct annual escrow analyses to ensure adequate funds, adjusting your monthly payment if needed based on current tax bills and assessment changes.

If you pay taxes independently, you can verify payments and balances through the Rock County Treasurer's online portal. Keep documentation of all tax payments for mortgage and refinancing purposes, as lenders will require proof of current tax status during loan processes.

How HonestCasa Helps
  • Understand whether your escrow is set correctly
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Section 6

Frequently Asked Questions

Q: When are Rock County property taxes due for the 2025 levy year? A: The first installment is due by January 31, 2026, with the second installment due later in 2026. Specific second installment dates vary by municipality within Rock County.

Q: What tax credits are available and do they require application? A: The primary credit is Wisconsin's Homestead Credit, an income-based program that requires annual application. This credit reduces your tax bill directly but has income limitations. Most credits are NOT automatic and must be applied for through the Wisconsin Department of Revenue.

Q: How does the Homestead Credit work? A: The Homestead Credit provides a direct reduction to your property tax bill based on your income level. It does not reduce your assessed value but instead caps how much your property tax can increase year-over-year. You must file annually with your state tax return to claim this credit.

Q: How often are properties reassessed in Rock County? A: Wisconsin requires assessments to reflect current market value annually. However, full reappraisals may occur every few years, with statistical updates in between. Contact your local assessor for your area's specific schedule.

Q: What are the penalties for late property tax payments? A: Wisconsin charges interest on delinquent property taxes, typically around 1% per month. Properties can eventually face tax sale proceedings if taxes remain unpaid for extended periods.

Q: Can I pay my property taxes online? A: Yes, Rock County accepts online payments including credit cards, though convenience fees may apply. Check the Rock County Treasurer's website for current payment options and fee schedules.

Q: How do special district taxes work? A: Special districts provide specific services like fire protection, libraries, or sanitation. These appear as separate line items on your tax bill and rates vary significantly based on which districts serve your property location.

Q: How do I appeal my property assessment? A: Assessment appeals in Wisconsin must be filed with your local Board of Review, typically meeting in May. You can also appeal to the Wisconsin Department of Revenue if unsatisfied with the local board's decision. Deadlines are strictly enforced.

Verified Sources

Backed by 10 Official Government Sources

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

01
County
Budget Information | Rock County, WIco.rock.wi.us
02
Newsletter - 2025 - Town Of Beloit, Witownofbeloitwi.gov
03
County
Mill Rates | Rock County, WIco.rock.wi.us
04
Tax Doc
Property Taxestownofrockwi.gov
05
County
Paying Property Taxes | Rock County, WIco.rock.wi.us
06
Tax Doc
City of Milton Tax Bills to be Mailed 12/12/16milton-wi.gov
07
DOR Homestead Credit - Wisconsin Department of Revenuerevenue.wi.gov
08
Tax Doc
Property Tax Assistance Information | Janesville, WIjanesvillewi.gov
09
County
Reports | Rock County, WIco.rock.wi.us
10
ANNEXATION APPLICATION Evansville, Wisconsinevansvillewi.gov
All sources verified as of 2025 Tax Year

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