N.H. Rev. Stat. Ann. § 75:3

Whenever a person owns or erects a building on land of another both may be taxed together as real estate to the owner of the land, provided a selectman or assessor, before or when taking the inventory, gives notice in writing to the landowner that such building is to be taxed to the landowner as real estate. An affidavit by the selectman or assessor giving the notice that such notice was given shall be evidence of the fact. The owner of the land shall have a lien on such building for the payment of the tax.