Mass. Gen. Laws ch. 51 § 42H
Registrars of voters in cities and towns shall receive completed affidavits of voter registration from registration agencies, from individuals and organizations conducting voter registration, through the United States mail, through the online portal and by hand delivery. Upon receipt of each completed affidavit, the registrars shall certify the receipt thereof and shall notify the registrant of the disposition of the affidavit. Said registrars shall add the registrant's name, address and effective date of registration to the annual register of voters in accordance with section forty-six, effective at the time set forth in section forty-two G; provided, however, that the state secretary may, by regulation adopted pursuant to section forty-seven C, provide that electronic transmission alone of the information contained in the affidavit of registration shall be sufficient for such purpose. The registrars may correct information supplied by the registrant to the extent necessary to maintain the integrity of their records. If an affidavit is incomplete or if it appears from the facts set forth in the affidavit that the registrant is not qualified to register as a voter, the registrars shall proceed in accordance with the provisions of section forty-seven. If an affidavit is dated by the registration agency or postmarked during the period when registration to qualify as a voter in a particular election is prohibited by section twenty-six, the registrant's name shall be added to the annual register for all subsequent elections and the registrars shall so notify such registrant. All records of voter registration held by registration agencies shall be available for inspection and copying by the registrars of the registrant's city or town or by summons in a legal proceeding.
Mass. Gen. Laws ch. 51, § 42H