Mass. Gen. Laws ch. 59 § 32
Lists filed under section 29 and books, papers, records and other data obtained under section 31A shall be open to the inspection of the assessors, the commissioner, the deputies, clerks and assistants of either the assessors or the commissioner and any designated private auditor of the commissioner or the assessors as may have occasion to inspect the lists, books, papers, records and other data in the performance of their official, contractual or designated duties, but so much of the lists, books, papers, records and other data as shows the details of the personal estate shall not be open to any other person except by order of a court. For purposes of this section, a "designated private auditor" shall be an individual, corporation or other legal entity selected by the commissioner or a city or town to value personal property or perform an audit which includes the assessing department of a city or town under any legal authority, including the examination of records under said section 31A, an audit under sections 40 or 42A of chapter 44 or an investigation under section 46A of said chapter 44 but only if the individual, corporation or other legal entity shall be compensated for the audit work pursuant to an arrangement under which neither the payment nor the amount of their fees and expenses for the work are contingent on either the results of the audit or whether the results withstand any appeal by a taxpayer. The lists shall be preserved by the assessors until the commissioner orders them destroyed. Nothing in this section shall prevent a person who submitted that information, or his designated representative, from inspecting or being provided a copy of the submission upon request.
Mass. Gen. Laws ch. 59, § 32