N.J. Stat. § 17:3B-7
Notwithstanding the provisions of R.S. 31:1-1, a lender may, subject to the criminal usury provisions of N.J.S. 2C:21-19, charge and collect interest under a revolving credit plan on outstanding unpaid indebtedness in the borrower's account under the plan at daily, weekly, monthly, annual or other periodic percentage rates as the agreement governing the plan provides or as established in the manner provided in the agreement governing the plan. If the applicable periodic percentage rate under the agreement governing the plan is other than daily, interest may be calculated on an amount not in excess of the average of outstanding unpaid indebtedness for the applicable billing period, determined by dividing the total of the amounts of outstanding unpaid indebtedness for each day in the applicable billing period by the number of days in the billing period. If the applicable periodic percentage rate under the agreement governing the plan is monthly, a billing period shall be deemed to be a month or monthly if the last day of each billing period is on the same day of each month or does not vary by more than four days therefrom.
Nothing in this section shall be construed to authorize the charging of interest on the amount of any accrued interest remaining unpaid on the account.
N.J.S. § 17:3B-7