Wis. Stat. § 102.63: Refunds by state.

Whenever the department shall certify to the secretary of administration that excess payment has been made under s. 102.59 or under s. 102.49 (5) either because of mistake or otherwise, the secretary of administration shall within 5 days after receipt of such certificate draw an order against the fund in the state treasury into which such excess was paid, reimbursing such payor of such excess payment, together with interest actually earned thereon if the excess payment has been on deposit for at least 6 months.