Wis. Stat. § 224.81: Limitation on actions for commissions and other compensation.

A person who is engaged in the business or acting in the capacity of a mortgage banker, mortgage loan originator, or mortgage broker in this state may not bring or maintain an action in this state to collect a commission, money, or other thing of value for performing an act as a mortgage banker, mortgage loan originator, or mortgage broker without alleging and proving that the person was licensed under this subchapter as a mortgage banker, mortgage loan originator, or mortgage broker when the alleged cause of action arose.