N.H. Rev. Stat. Ann. § 82:6

In determining the market value of the property and estate in this state of any such company, the department of revenue administration shall make careful inquiry into the condition of all of the property and estate, whether within or without the state, in order that the market value of all that portion of the property and estate of such company within this state, and subject to taxation hereunder, may be accurately fixed and determined.