N.H. Rev. Stat. Ann. § 43:4

They shall hear all parties who desire to be heard, and examine them and their witnesses under oath, which either of the selectmen may administer; they may adjourn when they deem it necessary; and they shall make their decision in writing, and cause the petition, order of notice, evidence of service and their decision to be filed in the town clerk's office and recorded at length upon the town records; and their decision shall be of no force or effect until the same is done.