N.H. Rev. Stat. Ann. § 80:70

When full redemption is made, the tax collector shall within 30 days after redemption notify the register of deeds of the act, giving the name of the person redeeming, the date when redemption was made, the date of the execution of the tax lien and a brief description of the real estate in question, together with the name of the person or persons against whom the tax was levied.