Section 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 shall be allowed under this section. Interest on amounts not paid when due, or interest on overpayments shall be equal to the sum of the simple interest amounts computed with respect to each calendar year, or a portion thereof, during which the underpayment or overpayment remains outstanding. Interest with respect to only a portion of a calendar year shall be determined on a pro rata basis based on the number of days the underpayment or overpayment remains outstanding during the 365-day calendar year. Upon certification by the commissioner, the state treasurer shall refund the overpayment with interest from the revenue of the specific tax.
   II. For purposes of this section, with respect to any calendar year, the term ""annual underpayment rate'' shall be determined by the commissioner and shall mean the underpayment rate specified in section 6621(a)(2) of the Internal Revenue Code of 1986 as in effect on the September 1 immediately preceding such calendar year plus 2 percentage points.
   III. For purposes of this section, with respect to any period, the term ""overpayment rate'' shall mean the underpayment rate determined under paragraph II with respect to such period year less 3 percentage points.
Source. 1985, 204:1. 1991, 163:4. 1992, 13:1. 1995, 268:1, eff. July 1, 1997.