N.H. Rev. Stat. § 80:37
For purposes of this section, "subsequent tax" shall mean any tax assessed upon the real estate subsequent to that for which it was sold by a municipality, a county or the state. The purchaser of real estate at any tax sale may pay to the collector any subsequent tax and the collector shall, within 30 days after such payment, notify the register of deeds thereof, giving the date and the amount of such payment and the name of the person so paying together with the date of the tax sale, the name of the person taxed and a description of the property sold as shown in the report of sale recorded in the registry of deeds. The collector of taxes shall receive $1 for such notice to the register of deeds of the payment of subsequent tax plus $1 to be paid to the register of deeds. The purchaser, within 30 days of payment of the subsequent tax, shall personally, or by certified mail, notify in writing any mortgagee who was notified of his purchase at the tax sale of this payment of the subsequent tax. The purchaser paying the subsequent tax shall receive the same fees prescribed for notifying the mortgagee of his or her purchase at the tax sale to be included in the costs to be paid by the person making redemption, except that when a town is a purchaser at a tax sale and the town pays a subsequent tax and the selectmen direct the collector of taxes as agent for the town to give notice of payment of a subsequent tax to any mortgagee who was notified of the purchase by the town at the tax sale, the collector shall be paid the sum of $5 for this service. Any amounts so paid on account of subsequent taxes, together with interest thereon at the rate of 14 percent per annum from the date of payment shall, in addition to the purchase price at the time of sale with accrued interest and costs, be paid by the person making redemption.
RSA 80:37
1851, 1125:1. CS 49:12. GS 55:12. GL 59:9. PS 61:11. 1925, 61:1. PL 66 :30. RL 80:30. 1943, 55:3. 1947, 187:2. 1949, 61:3. RSA 80:37. 1967, 313:1. 1970, 30:3. 1971, 512:3. 1981, 465:17. 1983, 285:5. 1985, 312:4. 1992, 54:1, eff. Jan. 1, 1993. 2018, 282:4, eff. Apr. 1, 2019.