RSA 21-J:28 Interest.

I. For all taxes administered by the department, interest on amounts not paid when due shall be computed at the annual underpayment rate determined from time to time pursuant to paragraph II from the prescribed payment date or original statutory due date to the date payment is actually made. Interest shall be allowed and paid at the annual overpayment rate determined from time to time pursuant to paragraph III upon any overpayment of taxes administered by the department. No interest shall be allowed or paid on amounts less than $10 unless specifically requested in writing. If any overpayment of tax administered by the department is refunded within 3 months after the due date or authorized extension date or within 3 months after the return is filed, whichever is later, no interest sh