N.H. Rev. Stat. Ann. § 72-B:7

Unless a bond or other security is required pursuant to RSA 72-B:5, excavation tax assessments levied under RSA 72-B:4 shall, on the date the excavating commences, create a lien upon the land on account of which it is made and against the owner of record of such land and shall continue for a period of 18 months following the date of assessment by the local assessing officials. All excavation tax assessments shall be subject to statutory collection proceedings against real estate as prescribed by RSA 80.