Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 43, § 7

A petition addressed to the city council, signed by qualified voters of the city to a number equal at least to ten per cent of the registered voters at the state election next preceding the filing of the petition and in the form provided in section eight may be filed with the city clerk who shall forthwith transmit the same to the registrars of voters, who shall within sixty days certify the signatures thereon in accordance with the provisions of law and return the petition to the city clerk.

The petition shall be filed with the city clerk at least one hundred and forty days before the date of the election at which the question proposed by the petition is to be submitted to a vote of the voters.