Wis. Stat. § 616.10: Exemption from taxation.

Every mutual designated a school benefit insurer under s. 616.03, every plan authorized under s. 616.06, and every corporation organized under s. 616.08 is declared to be a charitable and benevolent corporation, and its property, real, personal and mixed, and its income and property transferred to it, are exempt from taxation as provided in ss. 70.11, 71.26 (1) (a) and 71.45 (1) (a).