Wis. Stat. § 74.31: Failure to settle timely.

If the taxation district treasurer or county treasurer does not settle as required under ss. 74.23 to 74.30:

(1) Interest charge. The taxation district or county which has not settled shall pay 12 percent annual interest on the amount not timely paid to the taxing jurisdiction, including this state, to which money is due, calculated from the date settlement was required.

(2) Penalty. The taxing jurisdiction, including this state, to which money is due may demand, in writing, payment from the taxation district or county which has not settled. If, within 3 days after receipt of a written demand, settlement is not made, the taxation district or county shall pay the taxing jurisdiction, including this state, making the demand a 5 percent penalty on the amount remaining unpaid.