N.H. Rev. Stat. Ann. § 479-A:26

Without limiting the rights of any unit owner, actions may be brought by the manager or board of directors, in either case in the discretion of the board of directors, on behalf of 2 or more of the unit owners, as their respective interests may appear, with respect to any cause of action relating to the common areas and facilities or more than one unit. Service of process on 2 or more unit owners in any action relating to the common areas and facilities or more than one unit may be made on the person designated in the declaration to receive service of process.