N.Y. Suffolk County Tax Act § 40-c
The county treasurer shall not convey any lands sold for taxes if he shall discover before the conveyance that the sale was for any cause invalid or ineffectual to give title to the lands sold; but he shall cancel the sale and forthwith cause the purchase-money and interest thereon to be refunded out of moneys appropriated and available therefor to the purchaser, his representatives or assigns. If the error originated with the town officers the sum paid shall be a charge against the town from which the tax was returned, and the board of supervisors shall cause the same to be assessed, levied and collected and paid to the county treasurer.
If the county treasurer shall not discover that the sale was invalid until after a conveyance of the lands sold shall have been executed he may, on application of any person having any interest therein at the time of the sale, on receiving proof thereof, cancel the sale, refund out of moneys appropriated and available therefor to the purchaser, his representatives or assigns, the purchase-money and interest thereon, and recharge the town from which the tax was returned with the amount of purchase-money and interest from the time of sale which the county shall cause to be levied and paid to the county treasurer.
Where the county treasurer shall discover either before or after a conveyance that a sale to the county as provided by this article, was invalid or ineffectual as aforesaid, he shall cancel the same as aforesaid and charge or recharge the town as aforesaid but no refund shall be made. The county treasurer may also on his own motion, cancel a sale and charge or recharge the town as aforesaid, where the sale has been declared void by the courts, or where in the opinion of the county attorney filed with the county treasurer together with the evidence upon which such opinion is based, such sale would be declared void by the courts.
Nothing in this act contained shall affect or impair the power and authority of the board of supervisors or any other body or officer, as now provided by law, from compromising taxes and the payment thereof, or reducing the rates of interest or penalties now imposed by law for failure to pay any real property tax or water rate, or from correcting any erroneous assessment; but on and after the affective date of this act sales for unpaid taxes in the county of Suffolk shall be cancelled only by the county treasurer and in the manner provided by this section and sections forty-d and forty-e hereof.
N.Y. Suffolk County Tax Act § 40-c