Mass. Gen. Laws ch. 41, § 20: Selectmen; duties and oath; penalty

Section 20. Selectmen shall, upon the receipt and approval of the bond of a collector of taxes or treasurer, give written notice thereof to the assessors. The selectmen shall be assessors of taxes in towns which have not authorized the election of such officers; and before acting as assessors they shall take the oath required of assessors. A person elected a selectman who enters upon the performance of his duties before taking the oath of office shall forfeit not more than one hundred dollars.