Mass. Gen. Laws ch. 255D, § 28: Instruments indicating payment; mailing to buyer

Section 28. After payment of all sums for which the buyer is obligated under a retail installment sale agreement, if the notice of the security interest has been filed or recorded or if the buyer so requests, the holder of such contract shall mail to the buyer, at his last known address, good and sufficient instruments to indicate payment in full and to release all security in the collateral, if any.