Wis. Stat. § 70.501

Any assessor, or person appointed or designated under s. 70.055 or 70.75, who intentionally fixes the value of any property assessed by that person at less or more than the true value thereof prescribed by law for the valuation of the same, or intentionally omits from assessment any property liable to taxation in the assessment district, or otherwise intentionally violates or fails to perform any duty imposed upon that person by law relating to the assessment of property for taxation, shall forfeit to the state not less than $50 nor more than $250.