Section 13. The board, or a single member of the board acting pursuant to the authority outlined in section 1A shall make a decision in each appeal heard by it within three months from the close of the record including submission of briefs and may make findings of fact and report thereon in writing. In any appeal in which the hearing is officially recorded pursuant to section 10, or in any appeal from the commissioner of revenue other than cases heard under the small claims procedure pursuant to section 7B, the member may take an additional three months to issue a decision. In every decision granting an abatement without findings of fact and report which relates to a tax on land with one or more buildings thereon, the board shall, if so requested by the appellee in writing at the commencement of the hearing, state separately the value of the land and of each building.

Except in cases heard under the informal procedure authorized by section 7A, or under the small-claims procedure authorized under 7B, the board shall make such findings and report thereon if so requested by either party within ten days of a decision without findings of fact and shall issue said findings within three months of the request, provided, however, the board, in its discretion, may extend the time for issuing said findings and report for an additional period not to exceed three months, upon written notice to both parties setting forth the reason for the extension. In extraordinary circumstances or with consent of all parties to the proceeding, the board may have whatever additional time is necessary for issuance of such findings of fact and report. Such report may, in the discretion of the board, contain an opinion in writing, in addition to the findings of fact and decision. If no party requests such findings and report, all parties shall be deemed to have waived all rights of appeal to the appeals court upon questions as to the admission or exclusion of evidence, or as to whether a finding was warranted by the evidence. All reports, findings and opinions of the board and all evidence received by the board, including a transcript of any official report of the proceedings, all pleadings, briefs and other documents filed by the parties, shall be open to the inspection of the public; except that the originals of books, documents, records, models, diagrams and other exhibits introduced in evidence before the board may be withdrawn from the custody of the board in such manner and upon such terms as the board may in its discretion prescribe. The decision of the board shall be final as to findings of fact. Failure to comply with the time limits, as outlined above, shall not affect the validity of the board's decision.

From any final decision of the board except with respect to decisions of the board under sections 25 and 26 of chapter 65, an appeal as to matters of law may be taken to the appeals court by either party to the proceedings before the board so long as that party has not waived such right of appeal. A claim of appeal shall be filed with the clerk of the board in accordance with the Massachusetts Rules of Appellate Procedure which rules shall govern such appeal. The court shall not consider any issue of law which does not appear to have been raised in the proceedings before the board.

If the order grants an abatement of a tax assessed by the commissioner and the tax has been paid, the amount abated with interest computed in accordance with section 40 of chapter 62C, and if costs are ordered against the commissioner, the amount thereof, shall be paid to the taxpayer by the state treasurer. If the order grants an abatement of a tax assessed by the board of assessors of a town and the tax has been paid, the amount abated with interest at the rate of 8 per cent per annum from the time when the tax was paid, and if costs are ordered against a board of assessors, the amount thereof, shall be paid to the taxpayer by the town treasurer, and, if unpaid, execution therefor may issue against the town as in actions at law. If costs are ordered against a taxpayer execution shall issue therefor. The appeal to the appeals court under this section shall be the exclusive method of reviewing any action of the board, except action under sections 25 and 26 of chapter 65. For want of prosecution of an appeal in accordance with the provisions of this section the board, or, if the appeal has been entered in the appeals court, a justice of that court, may dismiss the appeal. Upon dismissal of an appeal, the decision of the board shall thereupon have full force and effect.