N.H. Rev. Stat. Ann. § 464-A:24

Every resident guardian who removes from the state, or who goes out of the state with intention of being absent more than a year, and every resident of another state who is appointed guardian within this state, shall forthwith appoint some person residing in the state as his agent to receive service of legal process against him as guardian. The appointment shall be made and renewed as in the case of agents of foreign administrators and with like authority and effect; and failure to appoint shall be cause for the removal of the guardian.