Massachusetts General Laws, Chapter 140, section 137
Registration and license.
A person who at the commencement of a license period, or who during any license period becomes, the owner or keeper of a dog six months old or over which is not duly licensed, and the owner or keeper of a dog when it becomes six months old during a license period, shall cause it to be registered, numbered, described and licensed during a license period, shall cause it to be registered, numbered, described and licensed until the end of such license period, and the owner or keeper of a dog so registered, numbered, described and licensed during any license period, shall, during any license period, in order to own or keep such dog after the beginning of the succeeding license period, shall, before the beginning thereof, cause it to be registered, numbered, described and licensed for such period. The registering, numbering, describing and licensing of a dog…(in all towns, except Boston) shall be in the office of the clerk thereof.
No town clerk…shall grant such license for any dog unless the owner thereof provides such town clerk either a veterinarian’s certification that such dog has been vaccinated (against rabies) in accordance with the provisions of section 145B, or has been certified exempt from such provision as hereinafter provided, or a notarized letter from a veterinarian that a certification was issued or a metal rabies tag bearing an expiration date indicating that such certification is still in effect.
A dog licensing official may grant an exemption from the provision of section 145B for any dog which has not yet attained the age of six months, any dog which the local board of health, for a specified period of time, declared exempt upon presentation of a veterinarian’s certificate stating that because of an infirmity, other physical condition, or regimen of therapy, that inoculation is thereby deemed inadvisable, or any dog in transit, or dog brought into the commonwealth, temporarily, for the sole purpose of showing in dog shows or exhibition.
… The owner or keeper of a licensed dog shall cause it to wear around its neck or body a collar or harness of leather or other suitable material, to which shall be securely attached a tag … upon which shall appear the license number, the name of the town issuing such license and the year of issue.