The power to tax property was granted to local government by Article VIII of the Wisconsin Constitution.
Each year, in December, the clerk in each Wisconsin municipality delivers a new tax roll to the treasurer. Attached to the roll is a warrant signed by the clerk. The affidavit orders the treasurer "to collect from each of the persons…or owners…of the real estate, or personal property described therein, the taxes set down opposite to their respective names…(Section 70.68, Wisconsin Statutes). The warrant also authorizes the sale of the property if the taxes are not paid.
The names and property descriptions combined in the tax roll come from the assessment roll, which is the official record of the taxable value of property within the municipality. The State Legislature has sole responsibility for laws pertaining to property tax assessments and tax collection, ensuring uniformity throughout the State. The Wisconsin Department of Revenue has been given broad supervisory and regulatory duties, primarily through the Bureau of Property Tax.
Chapter 70, Wisconsin Statutes, requires assessors to discover, list, and estimate marketable values for all taxable real and personal property each year as of January 1st. Information is collected to classify, define, and distinguish properties. In the City of Marshfield, the Assessor also maintains a sales database. The property information at the time of each sale is analyzed to help develop pricing tables for calculating the assessments.
The annual tax roll is absolute by law. Additional taxes are not collected from owners when properties sell for more than the assessed value during the year, and tax refunds are not given to owners when properties sell for less than the assessed values. However, it is the job of the Assessor to review assessed values annually. It is also the job of the assessor to grant or deny requests for property tax exemptions. According to Chapter 70.109, exemptions shall be strictly construed in every instance, with a presumption, the property in question is taxable - and the burden of proof is on the person claiming the exemption.
Wisconsin Act 39 (1991) changed Section 70.32 of the Wisconsin Statutes to require assessors to assess according to professionally acceptable appraisal practices. Professionally acceptable appraisal practices are ideals, beliefs, and procedures held and used by appraisers. Performance and technical standards and codes of behavior further define acceptable practices.
The Wisconsin Statutes also have rule standards that measure quality and performance;
The first, defined in Section 70.32, requires assessors to assess all non-agricultural property at full value.
Section 70.05 requires each municipality to assess property at full value at least once in every 5-year period.
Section 70.05 also requires the assessed values of all major classes of property (classes which include more than 5% of the full value of the taxation district) must be within 10% of the equalized value of the same major classes in the same year, at least once in the four-year review period.
When compliance is not met, the Wisconsin Department of Revenue orders special supervision for a revaluation under Statute 70.75 (3), with the municipality paying for associated costs.
Wisconsin’s technical standards are incorporated in the Wisconsin Property Assessment Manual. The standards are the product of research in property valuation, assessment administration and property tax policy from professional organizations such as the Wisconsin Association of Assessing Officers, the International Association of Assessing Officers, the Appraisal Foundation, etc. The manual specifies valuation methods and techniques, administrative practices, and policy and legal decisions.
Before the amount of property tax for individual properties can be determined, the amount of money to be spent by each of the various taxing jurisdictions (e.g. the state, county, municipality, school district, VTAE district) must be known.
Once the amount of tax to be levied by a jurisdiction has been determined, the tax levy must be divided among all of the municipalities (cities, towns or villages) with territory in that jurisdiction. The state tax levy is apportioned among all of the municipalities in the state - the county’s levy, among all of the municipalities in the county, the school levy, among all of the municipalities in the school district, etc.