Wis. Stat. § 77.981
The tax under s. 77.98 is imposed on the sale of taxable products at the rate of 0.25 percent of the sales price, except that the district, by a vote of a majority of the authorized members of its board of directors, may impose the tax at the rate of 0.5 percent of the sales price. A majority of the authorized members of the district's board may vote that, if the balance in a special debt service reserve fund of the district is less than the requirement under s. 229.50 (5), the tax rate under this subchapter is 0.5 percent. The 0.5 percent rate shall be effective on the next January 1, April 1, July 1 or October 1, and this tax is irrepealable if any bonds issued by the district and secured by the special debt service reserve fund are outstanding.
Wis. Stat. § 77.981