N.Y. Tax Law § 691
--(a) Timely mailing.--(1) If any return, claim, statement, notice, petition, or other document required to be filed, or any payment required to be made, within a prescribed period or on or before a prescribed date under authority of any provision of this article is, after such period or such date, delivered by United States mail to the tax commission, bureau, office, officer or person with which or with whom such document is required to be filed, or to which or to whom such payment is required to be made, the date of the United States postmark stamped on the envelope shall be deemed to be the date of delivery. This subsection shall apply only if the postmark date falls within the prescribed period or on or before the prescribed date for the filing of such document, or for making the payment, including any extension granted for such filing or payment, and only if such document or payment was deposited in the mail, postage prepaid, properly addressed to the tax commission, bureau, office, officer or person with which or with whom the document is required to be filed or to which or to whom such payment is required to be made. If any document or payment is sent by United States registered mail, such registration shall be prima facie evidence that such document or payment was delivered to the tax commission, bureau, office, officer or person to which or to whom addressed. To the extent that the tax commission shall prescribe by regulation, certified mail may be used in lieu of registered mail under this section. This subsection shall apply in the case of postmarks not made by the United States Post Office only if and to the extent provided by regulations of the tax commission. (2)(A) Any reference in paragraph one of this subsection to the United States mail shall be treated as including a reference to any delivery service designated by the secretary of the treasury of the United States pursuant to section seventy-five hundred two of the internal revenue code and any reference in paragraph one of this subsection to a postmark by the United States mail shall be treated as including a reference to any date recorded or marked in the manner described in section seventy-five hundred two of the internal revenue code by a designated delivery service. If the commissioner finds that any delivery service designated by such secretary is inadequate for the needs of the state, the commissioner may withdraw such designation for purposes of this article. The commissioner may also designate additional delivery services meeting the criteria of section seventy-five hundred two of the internal revenue code for purposes of this article, or may withdraw any such designation if the commissioner finds that a delivery service so designated is inadequate for the needs of the state. Any reference in paragraph one of this subsection to the United States mail shall be treated as including a reference to any delivery service designated by the commissioner and any reference in paragraph one of this subsection to a postmark by the United States mail shall be treated as including a reference to any date recorded or marked in the manner described in section seventy-five hundred two of the internal revenue code by a delivery service designated by the commissioner.