Wis. Admin. Code Trans § Trans 139.07
When a dealer accepts a vehicle in trade that is subject to an outstanding lien and agrees in the purchase contract to pay off the balance due the lien holder, the dealer shall pay the amount stated in the purchase contract due the lien holder, after any adjustments for any estimated trade-in lien payoff amounts pursuant to s. Trans 139.05(8g) within 14 days of taking delivery of the trade-in vehicle. The dealer shall be responsible for any interest that accrues, penalties assessed, late fees, or other charges made on the debt secured by the lien to the extent those penalties, fees or other charges result from the dealer delaying payment of the amount stated in the purchase contract to be due the lien holder beyond 14 days of taking delivery of the trade-in vehicle.
Wis. Admin. Code Department of Transportation Trans 139.07