N.Y. Comp. Codes R. & Regs. tit. 18, § 347.24
(b) In order to be eligible for closing, a child support case must meet at least one of the following criteria:
(3) parentage cannot be established because:
(4) the noncustodial parent's location is unknown and the child support enforcement unit has made diligent efforts using multiple sources, in accordance with section 347.7 of this Part, all of which have been unsuccessful, to locate the noncustodial parent: