N.H. Rev. Stat. Ann. § 282-A:141

Contributions unpaid on the date on which they are due and payable, as prescribed by the commissioner of the department of employment security in a rule, shall bear interest at the rate of one percent per month or part thereof until payment plus accrued interest is received by the commissioner. Interest collected pursuant to this paragraph shall be paid into the contingent fund provided in RSA 282-A:140.