N.J. Admin. Code § 18:26-10.8
In any case where the amount paid on account for the New Jersey transfer inheritance tax exceeds the amount of such tax due after final assessment has been made, the amount so overpaid will be refunded by the State Treasurer in the due course of business, provided, however, that all applications for a full or partial refund of the payment of the New Jersey transfer inheritance tax must be made within three years from the date of such payment, or from the date of the final determination of a court of competent jurisdiction, which establishes the fact that the decedent had no legal or equitable interest in the property on which the tax was assessed and erroneously paid, whichever is later; and provided, however, that no refund shall be made where such final determination occurs more than 20 years after the date of death of the decedent.
N.J. Admin. Code § 18:26-10.8