N.Y. Second Class Cities Law § 123
The board of contract and supply shall appoint a secretary to hold office during its pleasure, whose duty it shall be to keep a full journal of all the proceedings of the board and to perform such additional duties as may be required by the board, or by law or ordinance of the common council. Where any work or repairs needed to be done, or materials or supplies to be furnished for any office, court, board or department shall not exceed two hundred and fifty dollars in cost, the board of contract and supply may by general or special rule authorize the commissioner of public works, or the commissioner of public safety, or the secretary of the board, or any of them, to give written orders therefor and purchase the same. No materials or supplies shall be purchased for, or delivered by or upon the order of the commissioner to any officer, board, court, body or department of the city, except upon the requisition in writing from the officer, board, body or head of the department for which the same are required. The commissioner shall require a receipt in writing from each officer, board, body or head of the department for all supplies delivered to him or it by the commissioner or on his order, and he shall approve, in writing, all claims for any such materials or supplies purchased by him, before the same shall be presented to the comptroller for audit.
N.Y. Second Class Cities Law § 123