Mobile Home, Off-Highway Vehicle or Vessel. Registering a trailer in Florida requires a Florida trailer bill of sale form.A completed form to title and register a trailer is required. Keep copies of the bill of sale (FLHSMV recommends having it notarized), certificate of title or other type of transaction document showing it was sold. FL requires the bill of sale with the vin of the trailer on it. The Certificate of Origin will not hurt either.