Wis. Stat. § 614.80: Tax exemption.

Every domestic and nondomestic fraternal, except those that offer a health maintenance organization as defined in s. 609.01 (2) or a limited service health organization as defined in s. 609.01 (3) is exempt from all state, county, district, municipal and school taxes or fees, except the fees required by s. 601.31 (2), but is required to pay all taxes and special assessments on its real estate and office equipment, except as provided in ss. 70.11 (4) and 70.1105 (1).