Mass. Gen. Laws ch. 65 § 26
At any time within two months after the date of giving notice of any determination of value by the commissioner under section twenty-five, any person aggrieved by said determination may request the commissioner to alter such determination. If the commissioner alters or refuses to alter his determination, he shall notify the aggrieved person by mail. Failure of the commissioner to take action within two months from the receipt by him of such written request shall be deemed a refusal of the commissioner to alter his determination. At any time within two months after the mailing of such notice, or, if no action is taken, within two months after the time when such request is deemed to be refused, any person aggrieved by such alteration or refusal to alter may appeal to the appellate tax board. Said board shall appraise such property as has been valued by the commissioner at its value as of the date of death of the decedent, shall give notice of its decision to the commissioner and the appellant, and shall make return thereof to the probate court. Such return, when accepted by the court, shall be final except that any party aggrieved by such appraisal shall have an appeal on matters of law.
In all proceedings before the appellate tax board under this section, the commissioner shall receive notice and may be heard.
Mass. Gen. Laws ch. 65, § 26