City of Lake Mills, Wisconsin

On the shores of Rock Lake

2025 Full Revaluation Notice & Information

The City of Lake Mills has contracted with Catalis Assessing Services to perform a city-wide revaluation of all taxable property for assessment year 2025.  Accordingly, all Lake Mills property owners will soon receive a letter from the assessor indicating the start of this process. A copy of the letter can be found here. The purpose of a revaluation is not to collect more taxes.  Rather, it is intended to correct instances of unfairness that can occur over time.  Lake Mills has not conducted a revaluation in 27 years, and state law requires periodic revaluations to address value changes.  Over time, values in different neighborhoods and areas, and among different property types, change unequally.  Without a revaluation, relative assessments among properties become unfair, resulting in some owners paying too much in property taxes and others paying too little.

Reference the below sections on the process of a full revaluation, timeline, and other frequently asked questions. Sample documents of notices sent to property owners and definitions of important terms can be found at the bottom of this page.

Please reach out to the City's Assessor, Catalis, with questions regarding this process using the contact information on the right.


 What Happens During a Full Revaluation?

During a revaluation, all property assessments are updated to ensure that tax burden is distributed equitably. Each property's assessed value is examined and may be adjusted in order to reflect the current market and meet standards required by State Statute. For example, State Statute requires municipalities to adjust assessments if a majority of market sale prices are more than 10% above or below the assessment. This rule helps ensure that taxes are distributed fairly. 

The process begins with an initial visit by the City's Assessor to view exteriors of properties. Appointments will not be made prior to the first visit. When the Assessor first visits the property, a note will be left requesting that the property owner calls to set up an appointment for the Assessor to view the interior of the property.

To determine fair market value of a property, the Assessor may consider factors like cost to replace a property, sales of similar properties, present condition, rent it may earn, etc. These assessments do not set the amount of tax that a property is required to pay. Tax amounts are based on the tax levy and mill rate. See the below sections on what happens after a full revaluation for more explanation on this concept. 

 Why is the City of Lake Mills Doing a Full Revaluation?

Revaluation is completed to ensure that property values are accurate, fair, and meet requirements outlined in State Statute. The State requires that property assessments fall within 10% of fair market value at least once every five years. In 2022, 2023, and 2024 the assessment ratios were 81.49%, 72.88%, and 72.88%, respectively. The City has not completed a full revaluation since 1997. Updating assessments is a method used to meet this threshold. Reassessing properties can also help eliminate inequities within or between property classes.


The Assessor has certain statutory authority to enter land as described in Sections 943.13 and 943.15, Wisconsin Statutes.  The ability to enter land is subject to several qualifications and limitations, as described within the foregoing statutes. Copies of the applicable statutes can be obtained at public depositories throughout the State of Wisconsin, and from the State of Wisconsin Legislative Reference Bureau website ( or a copy may be obtained from the Municipal Clerk upon payment of applicable copying charges.

Exterior Inspections-Entry Refusal

Property owners may refuse entry to their property by providing notice to the Assessor. However, if a property owner denies a written request delivered by certified mail to view the exterior of the property, they shall not be allowed to contest the amount of the assessment before the Board of Review (Wis Stat 70.47(7)(aa)).

Interior Inspections-Entry Refusal

You have the right to refuse entry into the interior of your residence pursuant to section 70.05 (4m) of the Wisconsin statutes. Entry to view your property is prohibited unless voluntarily authorized by you. Notices of assessment were mailed in June of 2024 (also linked below) that contained a spot to indicate your consent or refusal of an interior visual inspection of your residence. This notice should be returned within 7 days via mail or email if you wish to refuse the inspection. Calling to make an appointment for an interior inspection will indicate your consent to allow the inspection.  Additionally, once the Assessor sends proper notification and a reasonable response period elapses, the Assessor can then conclude the property owners who do not provide written refusals have provided their implied consent.

Pursuant to section 70.05 (4m) of the Wisconsin statutes, you have the right to refuse a visual inspection of the interior of your residence and your refusal to allow an interior inspection of your residence will not be used as the sole reason for increasing your property assessment. Refusing entry to your residence also does not prohibit you from objecting to your assessment pursuant to section 70.47 (7) of the Wisconsin statutes. Each assessor shall create and maintain a database identifying all such property owners that deny entry to an assessor of the interior of the owner’s residence.

Property owners should know that if interior inspections are refused, the Assessor will use information available to them to assign a reasonable and accurate assessment to the best of their abilities. This may include information from the exterior inspection, similar property sale data, most recent assessment data of the property, etc. 

 What Happens After a Full Revaluation?

When all assessments have been completed, a "Notice of Assessment" will be sent to all property owners informing them of their new assessments. An "Open Book" conference will be held following this Notice, to give all property owners a chance to compare their information with neighboring property assessments, or to discuss any differences of opinion regarding assessed value that may exist. The next step will be the formal City of Lake Mills Board of Review. This Board will convene to hear oral testimony from taxpayers who feel, and can prove, their new assessment is substantially unfair, either by market value or by equity standards.

Updated assessments will go into effect January 1, 2025, and will not affect your tax bills received in December of 2024. 

 How Are Property Taxes Affected?

A revaluation does not mean that property taxes will increase. Assessments assigned by the City Assessor do not determine the amount of property taxes required to be paid. Tax bill amounts are determined by taking the assessed value of a property and multiplying it by the mill rate. Mill rates are determined by dividing the tax levy by the tax base of a taxing jurisdiction.  The below section on important terms explains these concepts in more detail.

To illustrate how the levy affects your assessment we’ll look at Badgertown; a community of two. Each property owner has a house valued at $100,000. Badgertown’s tax levy is $2,000; the amount needed to cover its expenses. Since each property owner owns 50% of the total property, they each pay 50% of the levy giving them each a tax bill of $1,000.

If property values in Badgertown go up 10%, then each property is assessed at $110,000. The amount they pay in taxes, however, remains the same. Each property owner still owns 50% of the total property in Badgertown and must pay 50% of the $2,000 tax levy or $1,000. And what if values start dropping? Property values might drop to $80,000 each but because they each still own 50% of the property, and Badgertown still needs to collect $2,000, they will continue to see a $1,000 property tax bill.

 Why Did Your Assessment Change if Your Home Hasn't Changed?

General economic conditions, such as interest rates, inflation, supply and demand, and changes in tax laws, will influence the market value of real estate. As property values change in the market place, those changes must be reflected on the Assessment Roll on an annual basis. Consequently, assessed values can go up or down even if you have made no changes to your property. 

 Important Terms

Revaluation: A process required by Wisconsin State Law that requires municipalities to ensure accurate assessments and fair property taxation. The last time any kind of revaluation was done in the City of Lake Mills was a market revaluation in 2019.

Assessed Value: An estimation of value given to a particular taxable property by the Assessor for purposes of taxation.

Market Value: The amount that a typical purchaser would be willing to pay for a particular property given that it is on the market for a reasonable amount of time and the sale is typical for that type of property in terms of financing and party relationship.

Assessment Ratio: The ratio of assessed value to market value. This ratio is determined by the Wisconsin Department of Revenue each year. Ex: If a home is assessed at $200,000 and the assessment ratio is 90%, the estimated fair market value would be approximately $222,200.

Tax Base: The total of all assessed values in the City of Lake Mills.

Taxing Jurisdiction: A geographical area defined for the purpose of taxation to provide services by an entity. Ex: The Lake Mills School District includes all or parts of the City and Town of Lake Mills, Town of Milford, Town of Aztalan, Town of Waterloo, etc and utilizes money from tax collection to provide services. For City of Lake Mills property owners, these include the City of Lake Mills, Jefferson County, Lake Mills Area School District, and Madison Area Technical College. These are listed on your tax bill and display the amount of tax levy that each jurisdiction receives.

Tax Levy: The total amount of money from property taxes that a taxing jurisdiction needs to receive to provide services.

Tax Rate or Mill Rate: The tax levy divided by the tax base. This rate is often expressed in dollars per thousand. The mill rate multiplied by the assessed value determines the amount of property tax that each property must pay.