N.J. Stat. § 40:63-81
After the passage of such ordinance by each of such municipalities, pursuant to the laws governing the same, the proper officers of each municipality so authorized by ordinance, may join in executing a joint contract in accordance with the provisions of the ordinance, and the several contracting municipalities are hereby authorized to do any and all acts necessary or advisable regarding the execution and recording of such joint contract.
Such contract when executed pursuant to the provisions of this article, shall be recorded in the office of the clerk of the county wherein such contracting municipalities are situated. If such municipalities are situated in different counties, then the contract shall be recorded with the clerk of the county in which each of the municipalities is situated.
N.J.S. § 40:63-81