Wis. Stat. § 76.06
In any matter material to the valuation, assessment or taxation of property under this subchapter, the department may, in its discretion, exercise any and all of the powers conferred upon it by ss. 73.03 and 73.04(1); and every state, county, city, village, town and other public officer shall make return to the department in such form as it shall prescribe, of all information it shall call for. Persons serving the process of the department shall receive the same compensation allowed by law to sheriffs for similar service; and persons appearing before the department in obedience to its summons shall, in the discretion of the department, receive the same compensation as a witness in the circuit court; such fees and compensation to be audited by the department of administration on the certificate of the department, and charged to the proper appropriation for the department of revenue. The records, books, accounts and papers of any company defined in s. 76.02 to be assessed under this subchapter, except as otherwise provided, shall be subject to the visitation, inspection and examination by said department or by such person as it may designate for that purpose.
Wis. Stat. § 76.06