N.Y. Lien Law § 16
No assignment of a contract for the performance of labor or the furnishing of materials for a public improvement, or of the money, or any part thereof, due, or to become due, therefor, nor an order drawn by the contractor or sub-contractor upon the public corporation, or the head of the department or bureau having charge of the construction or demolition of such public improvement, or the financial officer of the public corporation, or other officer or person charged with the custody and disbursement of the corporate funds applicable to the contract for such public improvement, shall be valid unless such assignment or order, or a copy thereof, be filed within twenty days after the date of such assignment of contract, or such assignment of money, or such order, with the head of the department or bureau having charge of such construction or demolition, and with the financial officer of the public corporation or other officer or person charged with the custody and disbursement of the corporate funds applicable to the contract for such public improvement, and such assignment or order shall have effect and be enforceable from the time of such filing, and no such assignment or order shall have any validity until the same shall have been so filed, and every such assignment or order, not filed, shall be absolutely void as against a subsequent assignee in good faith and for valuable consideration, whose assignment or order is first duly filed. The financial officer of the public corporation, or other officer or person with whom the assignment order, or copy thereof, is filed, shall enter the facts relating to the same in the lien book or other book provided for such purpose.
N.Y. Lien Law § 16