Mass. Gen. Laws ch. 185 § 30
If a complaint is made subject to an existing recorded mortgage, the holder of which has consented thereto, or subject to a recorded lease for a term exceeding seven years, or if the registration is to be made subject to such a mortgage or lease executed after the time of the complaint and before the date of the transcription of the judgment, the plaintiff, before a judgment of registration is entered, shall, if required by the court, file a certified copy of such mortgage or lease, and shall cause the original, or, in the discretion of the court, a certified copy thereof, to be presented for registration; and no registration fee shall be charged for registering such original mortgage or lease or such certified copy.
Mass. Gen. Laws ch. 185, § 30