N.Y. County Law § 625
The board of supervisors shall have power to create the office of county purchasing agent, who shall be appointed for the term for which the membership of such board appointing him was elected. Except as otherwise provided by law, he shall make all purchases and contracts for supplies for the various county offices, buildings, institutions and grounds of the county, and shall let to public advertisement and bid all purchases when so required by section one hundred three of the general municipal law. He shall prescribe the form of requisitions, and of receipts for supplies delivered without requisition. No claim shall be audited and paid without the requisition or delivery receipt being attached thereto. He shall be the custodian of all vouchers, requisitions, receipts and other papers pertaining thereto which shall be open to public inspection. He shall upon dates to be fixed by the board and covering periods to be specified by it furnish to the county treasurer and to the clerk of the board of supervisors verified statements of all purchases together with the quantity and price and shall furnish to the board of supervisors such additional statements as the board may direct. He shall perform such additional and related duties as may be prescribed by law and directed by the board of supervisors.
N.Y. CountyLaw § 625