Nobody is required to let an assessor into their home, though you'll probably want to. New Hampshire municipalities are required by statute to levy taxes proportionally on real estate. Most, if not all, towns hire assessing firms for this purpose.

An appraiser has the authority to: Enter private land for appraisal purposes unless the owner or lawful occupant of that property objects to the appraiser's entry. The owner's objection could be expressed orally, in writing, or by conspicuous placement of “no trespassing” signs on the property.