Wis. Stat. § 76.17: Immaterial irregularities.

No tax assessed upon any of the general property of the state and no average rate determined by said department as herein required, shall be held invalid on account of any assessment or tax roll not having been made or proceedings had within the time required by law, or on account of the property having been assessed without the name of the owner, or in the name of any corporation or person other than the owner, or on account of any other irregularity, informality or omission, if the method and manner of ascertaining and determining the average rate of taxation on property in this state is in substantial accordance with law.