Division of Law Enforcement. RECREATIONAL. The title or transfer document must include the buyer's and seller's names and signatures and the mileage and sales price.A Massachusetts trailer bill of sale form personifies agreeableness between two (2) parties while determining how to conduct a transaction. General Bill of Sale – This form would usually be used to provide proof of sale and purchase between two private parties in the sale of personal items. A Bill of Sale stating the trailer's value. This can be a self-generated document if necessary.