N.H. Rev. Stat. § 14-A:3

I. A member of the general court shall be entitled to a mileage allowance at the rates specified by RSA 14:15-a for miles actually traveled while on legislative business. Except as otherwise specifically provided only travel paid out of legislative travel funds shall be considered legislative travel. The presiding officer of the house of representatives or senate, or his respective designee, shall determine what constitutes travel on legislative business for the members of his respective house. II. In addition to legislative mileage, the president of the senate or the speaker of the house may authorize payment of expenses incident to travel by a member of his respective house on official legislative business, provided that no additional expenses shall be paid for such business at Concord on a day when the general court meets. III. Any member of the general court who travels on official state business which is not legislative business as determined by the president of the senate or the speaker of the house shall be reimbursed for his actual travel by the appropriate state agency at the same rate provided for state employees. Except as otherwise specifically provided, no mileage paid out of executive agency funds shall be considered legislative business. IV. The provisions of this section shall not apply to members of the general court traveling on official business pursuant to a specific statute which provides for legislative mileage. In such cases, the members shall receive legislative mileage at the rate provided for in RSA 14:15-a, notwithstanding that the mileage is paid out of executive agency funds.