Chapter 5-11 Section 5 Updates Changes Made to Sales Tax A Massachusetts dealer may not receive any trade-in deduction to the taxable sales price on any vehicle to be registered and owned by the dealership. Whenever a dealership is registering a vehicle in its own name, a copy of the dealer's invoice that shows the total cost of the vehicle (including accessories) must be submitted to the RMV at the time of registration. The tax due is calculated based on this total cost, and no credit is given for any trade-in. 11/08 5:64