N.Y. Comp. Codes R. & Regs. tit. 8, § 90.6
(c) The board of trustees of every library system shall:
(18) at its discretion, establish a petty cash fund for the purpose of making payment in advance of authorization of properly itemized bills for materials, supplies or services furnished to the library system calling for immediate payment on delivery.
The following accounting procedures shall be employed by cooperative library systems and reference and research library resources systems.