N.Y. Second Class Cities Law § 92
The commissioner of public works shall have full power and authority to require the owner of property abutting upon a street to repair any sidewalk in front thereof or bring the same to true grade, and to remove the snow and ice therefrom. Where the owner of such property shall fail or neglect to repair any sidewalk or bring the same to true grade for five days after written notice so to do has been served on him, either personally or by delivering the same at his residence, or if he be a non-resident by mailing the same to him at his last known place of residence, or if the name of the owner or his place of residence can not be ascertained after due diligence, by posting the same in a conspicuous place upon the premises; or where the owner of any such premises shall fail or neglect to remove snow and ice from any such sidewalk after the same has remained thereon for more than twelve hours, and the commissioner shall have repaired such sidewalk or brought the same to grade or removed the ice or snow therefrom, a bill for the expenses incurred thereby shall be presented to the owner personally or by leaving the same at his residence or, if he be a non-resident, by mailing the same to him at his last known place of residence, or, if the name of such owner or his place of residence can not be ascertained after due diligence, by posting the same in a conspicuous place on the premises; and, if he shall fail to pay the same within ten days thereafter, the commissioner shall file each year immediately preceding the time for making the annual assessment-roll his certificate of the actual cost of the work, together with a statement as to the property in front of which the repairing or grading or cleaning was done, with the assessors of the city, who shall, in the preparation of the next assessment-roll of general city taxes, assess such amount upon such property, and the same shall be levied, corrected, enforced and collected in the same manner, by the same proceedings, at the same time, under the same penalties and having the same lien upon the property assessed as the general city tax and as a part thereof.
N.Y. Second Class Cities Law § 92