Mass. Gen. Laws ch. 186 § 24

(c) A tenant or co-tenant to whom this section applies shall be discharged from liability for rent or use and occupancy for 30 days or 1 full rental period after the quitting date, whichever last occurs, to the extent that a rental agreement and applicable law may otherwise impose such liability beyond the quitting date. Such tenant or co-tenant shall be entitled to a refund of any prepaid rent for any period thereafter. The tenant or co-tenant shall receive a full and specific statement of the basis for retaining any of the security deposit together with any refund due in compliance with section 15B within 30 days of the conclusion of the tenancy and the delivery of full possession of the leased premises by all occupants to the landlord.