Section 7. Any party taking an appeal to the board, hereinafter called the appellant, from a decision or determination of the commissioner or of a board of assessors, hereinafter referred to as the appellee, shall file a petition with the clerk of the appellate tax board and serve upon said appellee a copy thereof in the manner provided in section 9. No petition shall relate to an assessment on more than one parcel of real estate, except where the board shall specifically permit otherwise. Upon such appeal, the petition shall set forth specifically the facts upon which the party taking an appeal, hereinafter called the appellant, relies, together with a statement of the contentions of law which the appellant desires to raise. The appellant shall state upon the petition the address at which service of any pleading, motion, order, notice or process in connection with the appeal can be made upon him. Within such time as the board by its rules may prescribe, the appellee shall file with the board an answer denying or admitting each and every allegation of fact contained in the petition; except that, in an appeal under section 64 or 65 of chapter 59, if the appellee desires to raise no issue other than the question whether there has been an overvaluation or improper classification of the property on which the tax appealed from was assessed, no answer need be filed. If no answer is filed in such a case, the allegation of overvaluation or improper classification of such property shall be held to be denied and all other material facts alleged in the petition admitted. If an answer is filed, a copy shall be served upon the appellant, in the manner provided in section 9. The party taking the appeal shall at the time of filing the petition pay to the clerk an entry fee for each appeal from a decision of the commissioner, or, in the case of an appeal from a decision of a board of assessors, an entry fee where the assessed fair cash valuation of the real property, or personal property, or both, the tax on which is sought to be abated, is $50,000 or less; or an entry fee where such assessed fair cash valuation is in excess of $50,000. The commissioner of administration shall annually determine the amounts of such entry fees under the provisions of section 3B of chapter 7. Except as provided in section 12C of this chapter, the board shall not consider, unless equity and good conscience so require, any issue of fact or contention of law not specifically set out in the petition upon appeal or raised in the answer. At any time before the decision upon the appeal by the board or by the appeals court under section 13, the appellee may abate the tax appealed from, in whole or in part, or change its determination subject to the provisions of section 37A or 37C of chapter 62C.

If any petition, including any petition, statement or appeal filed under this section or section 7A or 7B, is, after the period allowed for filing appeals with the board, delivered by United States mail, or by such alternative private delivery service as the board may by rule permit, to the board, the date of the United States postmark, or other substantiating mark permitted by rule of the board, affixed on the envelope or other appropriate wrapper in which such petition is mailed or delivered shall be deemed to be the date of delivery, if such petition was mailed in the United States in an envelope or other appropriate wrapper, first class postage prepaid, or delivered to such alternative private delivery service, properly addressed to the board. As used in this section, ''United States postmark'' shall mean only a postmark made by the United States post office.

In the case of an appeal relating to property classified as either residential greater than eight units, or commercial or industrial, and which is assessed for more than $200,000 in the previous fiscal year, upon the written request of the appellee, the appellant shall file with the board an income and expense statement for the most recent year preceding the valuation date at issue in the appeal, completed under oath, within 40 days of such request.