N.H. Rev. Stat. Ann. § 32:25

Any city, town, unincorporated town, unorganized place, school district, village district, or county may budget receipts and expenditures, raise and appropriate revenues, and assess taxes on a biennial budget basis consisting of one distinct 24-month fiscal year or 2 distinct 12-month fiscal years. The governing body may allow for the carry over of funds from the first fiscal year of the biennium to the second.