Mass. Gen. Laws ch. 167D, § 3
A bank may receive demand, time and other types of deposits without limitation and upon such terms and conditions as may be agreed upon between the depositor and the bank. Such deposits may include, but shall not be limited to, the types of deposits described in subsections (a) to (c), inclusive.
(a) Any bank or federally-chartered bank may receive deposits in the name of 2 or more persons as joint tenants, payable to 2 or more persons or the survivor or survivors of them, and any part or all of the deposits and interest represented by joint accounts may be withdrawn, assigned or transferred in whole or in part by any of the individual parties. Payments to any of the parties to a joint account while all of them are living shall discharge the liability of the bank or federally chartered bank to all persons and, in the event of the death of any of them, the bank or federally chartered bank shall be liable only to the survivor or survivors and the payment to any of the survivors shall discharge the liability of the bank or federally chartered bank to all persons.
The surviving owner or owners of a joint account may maintain the balance of the account in the amount appearing at the time of the decease of a joint owner and such bank or federally chartered bank may allow interest additions and accumulations thereon.
Such deposits or any part thereof, or any interest thereon, may be paid to any of such persons or to any assignee or pledgee of any of such persons, whether the other such persons be living or not; provided, however, that they are not then attached at law or in equity in a suit against any such person, and the bank or federally chartered bank then has no notice in writing of any assignment or pledge of the account by any of such persons to any person other than the person to whom payment is being made hereunder. All such payments shall be valid and discharge the liability of the bank to all persons.