Mass. Gen. Laws ch. 43B § 3
The adoption of a charter for any city or town under sections two and three of Article LXXXIX of the Amendments to the Constitution and the revision of any charter so adopted shall be initiated by filing with the board of registrars of voters of the city or town a petition signed by at least fifteen per cent of the number of registered voters residing in said city or town at the preceding state election. Such petition may consist of a number of separate sheets, but each sheet shall be in substantially the form prescribed therefor in section fifteen and shall be signed and completed in accordance with the instructions contained therein. The city or town clerk shall furnish forms for such petition to any registered voter of the city or town requesting the same. Within ten days from such filing, the board shall check each name to be certified by it on the petition, shall certify thereon the number of signatures so checked which are names of registered voters in the city or town, and shall report the results to the city council or board of selectmen, as the case may be, by filing its report with the city or town clerk. Only names so checked shall be deemed to be names of registered voters for purposes of such petition. The board need not certify more than one hundred and forty per cent of the number of names required to file a petition, and names not certified in the first instance shall not thereafter be certified on the same petition.
The sheets constituting a petition need not be filed at the same time. For the purposes of this section and of section three of said Article LXXXIX, such a petition shall be deemed to be filed whenever the persons responsible for its filing notify the board in writing that the filing is complete. Before receiving such notice, the board may, but shall not be required to, certify signatures on the sheets of the petition already filed.
Objections to the sufficiency and validity of the signatures on any such petition as certified by the board of registrars of voters shall be made in the same manner as provided by section seven of chapter fifty-five B, within two working days after the filing of the aforementioned certification report by the board.
Mass. Gen. Laws ch. 43B, § 3