N.H. Rev. Stat. Ann. § 37:16

Any town which shall have adopted the provisions of this chapter may at the annual or a special meeting, under a proper article in the warrant, vote to authorize the selectmen to appoint the town manager to also be collector of taxes within and for such town and to fix his compensation therefor. In such case and while such vote is in effect, the town shall not vote to elect a collector of taxes.