N.H. Rev. Stat. Ann. § 546-B:34

If the obligor's employer receives 2 or more income-withholding orders with respect to the earnings of the same obligor, the employer satisfies the terms of the orders if the employer complies with the law of the state of the obligor's principal place of employment to establish the priorities for withholding and allocating income withheld for 2 or more child support obligees.