N.H. Rev. Stat. Ann. § 450:3

If any of the charges referred to in this chapter shall remain unpaid for 60 days, the lienholder may sell such motor vehicle or aircraft or house trailer at public sale, and the proceeds, after first paying the expense of sale, shall be applied in payment of the charges, the balance, if any, to be paid to the debtor. Notice of such sale shall be given and record made as provided in RSA 444:3, 4 and 6.