N.Y. Second Class Cities Law § 68
The treasurer may appoint, to hold office during his pleasure, a deputy and such other subordinates as may be prescribed by the board of estimate and apportionment. In case of the absence or disability of the treasurer, or of a vacancy in the office, the deputy shall discharge the duties of the office until the treasurer returns, his disability ceases or the vacancy is filled. The treasurer and deputy treasurer, before entering upon the discharge of the duties of their respective offices, shall each execute and file with the city clerk, an official undertaking in such penal sum as may be prescribed by the common council. Such undertaking, when approved as provided by law, shall have the same force and effect, and shall be filed and recorded in the office of the county clerk of the county in which the city is located in the same manner as is required in the case of an undertaking of a town collector.
N.Y. Second Class Cities Law § 68