N.Y. Real Property Tax Law § 421-K
2.
(a) Such buildings within such city shall be exempt for a period of one year to the extent of one hundred percent of the increase in assessed value attributable to such reconstruction, alteration or improvement and for an additional period of seven years subject to the following:
(b) No such exemption shall be granted for reconstruction, alterations or improvements unless:
7.
(a) The enactment of a local law in such city may: