Wis. Stat. § 70.50: Delivery of roll.

Except in counties that have a county assessment system under s. 70.99 and in cities of the 1st class and in 2nd class cities that have a board of assessors under s. 70.075 the assessor shall, on or before the first Monday in May, deliver the completed assessment roll and all the sworn statements to the clerk of the town, city, or village, who shall file and preserve them in the clerk’s office. On or before the first Monday in April, a county assessor under s. 70.99 shall deliver the completed assessment roll and all sworn statements to the clerks of the towns, cities, and villages in the county, who shall file and preserve them in the clerk’s office.