New York Consolidated Laws, Tax Law - TAX § 1420. Limitations of time

(a) The provisions of the civil practice law and rules or any other law relative to limitations of time for the enforcement of a civil remedy shall not apply to any proceeding or action taken by the state or the commissioner of taxation and finance to levy, appraise, assess, determine or enforce the collection of any tax or penalty provided by this article.  No assessment of additional tax shall be made after the expiration of more than three years from the date of the filing of a return;  provided, however, that where no return has been filed as provided by law or in the case of a willfully false or fraudulent return, the tax may be assessed at any time.

(b) Where, before the expiration of the period prescribed herein for the assessment of additional tax, a taxpayer has consented in writing that such period be extended, the amount of such additional tax due may be determined at any time within such extended period.  The period so extended may be further extended by subsequent consents in writing made before the expiration of the extended period.  If a taxpayer has consented in writing to the extension of the period for assessment, the period for filing an application for a refund pursuant to section fourteen hundred twelve shall not expire prior to six months after the expiration of the period within which an assessment may be made pursuant to the consent to extend the time for assessment of additional tax.