N.J. Stat. § 54:38-5
All taxes imposed by R.S. 54:38-1 and R.S. 54:38-2 shall become due at the date of death of the decedent and if not paid before the expiration of nine months from the date of the death of the decedent shall bear interest at the rate of ten percent per annum from the expiration of said nine months until paid, unless an extension of time to file the federal estate tax return is granted, in which case the director may reduce the interest rate to six percent per annum until the expiration of the extension; provided however, that if the decedent shall have heretofore died or shall hereafter die while a member of the Armed Forces of the United States, no such tax shall commence to bear such interest until the expiration of nine months after receipt of official notification of the death of the decedent by the husband, wife, father, mother, or next of kin of such decedent. The director may, for cause shown, extend the time for payment with interest at the rate of ten percent per annum for such period as the circumstances, in his discretion, may require.
N.J.S. § 54:38-5