N.H. Rev. Stat. Ann. § 515:14

If, in an action before a municipal court, the defendant pleads a setoff or files a setoff with the general issue which exceeds the jurisdiction of the court, and accompanies it with an affidavit that the claims mentioned in the setoff are, in his belief, justly due and owing to him, no further proceedings shall be had before the municipal court than to record the plea and setoff, and, if the plaintiff so elects, to enter a nonsuit.