Mass. Gen. Laws ch. 203A § 3
An account of the administration of each common trust fund shall be prepared annually and shall be audited by an independent certified public accountant and a copy of the account and the audit report shall be made available to any interested party upon written request, free of charge. A fiduciary may file an application for allowance of any such account, but shall not be required to file such application unless ordered by said probate court on motion of any interested party to such account or on motion of the court. A proceeding for the allowance of an account brought pursuant to this chapter in the probate and family court department of the trial court may be initiated by filing a petition and giving notice as provided under sections 1-401 and 1-403 of chapter 190B and section 1-404 of said chapter 190B shall apply to such proceeding. The allowance of any such account shall be conclusive as to all matters shown therein upon all persons then or thereafter interested in the funds invested in said common trust fund.
Mass. Gen. Laws ch. 203A, § 3