N.H. Rev. Stat. Ann. § 76:14

If the selectmen, before the expiration of the year for which a tax has been assessed, shall discover that the same has been taxed to a person not by law liable they may, upon abatement of such tax and upon notice to the person liable for such tax, impose the same upon the person so liable. And if it shall be found that any person or property shall have escaped taxation the selectmen, upon notice to the person, shall impose a tax upon the person or property so liable.