N.H. Rev. Stat. Ann. § 378:26

A copy of such list for the preceding year shall be filed with the commission and the department of energy, in such form and under such regulations as they may prescribe. Such list, together with the books, records and papers of the carrier so far as relevant, shall be open at all times to the inspection of the commission, who shall examine the same whenever they deem it necessary to the due enforcement of this title.