Mass. Gen. Laws ch. 142 § 3B
A person duly licensed in the commonwealth as a master plumber or as a master gas fitter may apply to the examiners for a certificate of a plumbing corporation or for a certificate of a gas fitting corporation or a certificate of a plumbing partnership or a certificate of a gas fitting partnership upon payment of a fee and a biennial renewal fee, the amounts of which shall be determined annually by the commissioner of administration under the provision of section three B of chapter seven for the filing thereof. A certificate of a plumbing corporation shall authorize a master plumber to conduct the plumbing and gas fitting business as a corporation, a certificate of a gas fitting corporation shall allow a master gas fitter to conduct the gas fitting business as a corporation, provided, that in a plumbing corporation the master plumber and in a gas fitting corporation the master gas fitter is an officer of the corporation organized under the laws of the commonwealth to engage in the business of plumbing or in the business of gas fitting. A certificate of plumbing partnership shall authorize a master plumber to conduct the plumbing and gas fitting business as a partnership, a certificate of a gas fitting partnership shall authorize a master gas fitter to conduct the gas fitting business as a partnership; provided, that all partners in a plumbing partnership are master plumbers and in a gas fitting partnership all partners are master gas fitters. For the purpose of this section, a gas company, as defined in section one of chapter one hundred and sixty-four, shall be deemed a gas fitting corporation.
Mass. Gen. Laws ch. 142, § 3B