Wis. Stat. § 342.33: Sale of vehicle used as taxicab.

No person shall sell or exchange, authorize or direct the sale or exchange of, or offer for sale or exchange any motor vehicle which the person knows has been used as a taxicab or for public transportation unless the certificate of title for such vehicle has been stamped by the department with the words “This motor vehicle has previously been used as a taxicab or for public transportation” and unless such certificate of title is exhibited by the vendor to the vendee before the sale of such vehicle is consummated. Any person who violates this section may be required to forfeit not more than $1,000.