N.H. Rev. Stat. Ann. § 135-C:16

Subject to RSA 135-C:17, any client receiving service or treatment on a voluntary basis may at any time withdraw from the service or treatment or from any specific form of treatment. The commissioner shall adopt rules, pursuant to RSA 541-A, relative to the rights of minors to withdraw from service or treatment. The commissioner may adopt rules, pursuant to RSA 541-A, which limit the right of a client to withdraw completely from a receiving facility at night or on weekends and holidays. When a withdrawal is made against medical advice, the client shall be notified in writing of that fact and a copy of the notice shall be made a part of the client's record.