N.J. Stat. § 54:32B-16
Every person required to collect any tax imposed by this act shall keep records of every purchase, purchase for lease, sale or amusement charge or occupancy and of all amounts paid, charged or due thereon and of the tax payable thereon, in such form as the director may by regulation require. Such records shall include a true copy of each sales slip, invoice, receipt, statement or memorandum upon which subsection (a) of section 12 requires that the tax be stated separately. Such records shall be available for inspection and examination at any time upon demand by the director or his duly authorized agent or employee and shall be preserved for a period of four years, except that the director may consent to their destruction within that period or may require that they be kept longer.
N.J.S. § 54:32B-16