The questions we get at the Law Library about secretly recording conversations usually refer to private parties: family members, neighbors, or landlords and tenants, so that is what we focus on in this guide.
New Hampshire is a "two-party" or "all-party" state where every party to a conversation has to agree to the recording. The New Hampshire statute is RSA 570-A, Wiretapping and Eavesdropping. Intentional violations of RSA 570-A can result in a class B felony or a misdemeanor, as well as money damages.
New Hampshire law is stricter than federal and many other states' laws. Although it's about criminal law, the book Criminal Practice and Procedure has an excellent, detailed comparison of New Hampshire and federal law on eavesdropping or wiretapping, and does include some discussion about actions by private parties. In The Law of Electronic Surveillance, there are chapters on surveillance by communications companies, and interspousal and intrafamilial surveillance.
Two First Circuit (New Hampshire is part of the First Circuit) cases have affirmed our First Amendment right to record police officers under certain circumstances.
Please remember that this guide is for information purposes only and is not comprehensive. It is intended as a starting point for research, to illustrate the various sources of the law, and to provide guidance in their use. NH Law About ... is not a substitute for the services of an attorney.