N.J. Stat. Ann. § 40A:2-62

The governing body, by bond ordinance or resolution, may establish a reserve fund to provide for payment of principal of and interest on any obligations and appropriate thereto any unappropriated funds arising from other than tax sources, or any other moneys made or to be made available by budget or otherwise. A certified copy of such ordinance or resolution shall be filed in the office of the director. The establishment of such fund shall be irrevocable so long as the obligations with respect to which it was created are outstanding or unpaid. Such fund may be invested in the same manner as other moneys of the local unit unless otherwise provided.