N.Y. GCT Law § 63

§ 63. Limitations on assessment.--(a) General.--Except as otherwise\nprovided in this section, any tax under this local law shall be assessed\nwithin three years after the return was filed (whether or not such\nreturn was filed on or after the date prescribed).\n (b) Time return deemed filed.--(1) Early return.--For purposes of this\nsection a return of income tax, except withholding tax, filed before the\nlast day prescribed by law or by regulations promulgated pursuant to law\nfor the filing thereof, shall be deemed to be filed on such last day.\n (2) Return of withholding tax.--For purposes of this section, if a\nreturn of withholding tax for any period ending with or within a\ncalendar year is filed before April fifteenth of the succeeding calendar\nyear, such return shall be deemed to be filed on April fifteenth of such\nsucceeding calendar year.\n (c) Exceptions.--(1) Assessment at any time.--The tax may be assessed\nat any time if--\n (A) no return is filed,\n (B) a false or fraudulent return is filed with intent to evade tax, or\n (C) the taxpayer fails to comply with section thirty-nine in not\nreporting a change or correction increasing his federal taxable income\nas reported on his federal income tax return, or the execution of a\nnotice of waiver and the changes or corrections on which it is based or\nin not reporting a change or correction which is treated in the same\nmanner as if it were a deficiency for federal income tax purposes, or in\nnot filing an amended return.\n (2) Extension by agreement.--Where, before the expiration of the time\nprescribed in this section for the assessment of tax, both the\nadministrator and the taxpayer have consented in writing to its\nassessment after such time, the tax may be assessed at any time prior to\nthe expiration of the period agreed upon. The period so agreed upon may\nbe extended by subsequent agreements in writing made before the\nexpiration of the period previously agreed upon.\n (3) Report of changed or corrected federal income.--If the taxpayer\nshall, pursuant to section thirty-nine, report a change or correction or\nfile an amended return increasing his federal taxable income or report a\nchange or correction which is treated in the same manner as if it were a\ndeficiency for federal income tax purposes, the assessment (if not\ndeemed to have been made upon the filing of the report or amended\nreturn) may be made at any time within two years after such report or\namended return was filed. The amount of such assessment of tax shall not\nexceed the amount of the increase in city tax attributable to such\nfederal change or correction. The provisions of this paragraph shall not\naffect the time within which or the amount for which an assessment may\notherwise be made.\n (4) Deficiency attributable to net operating loss carryback.--If a\ndeficiency is attributable to the application to the taxpayer of a net\noperating loss carryback, it may be assessed at any time that a\ndeficiency for the taxable year of the loss may be assessed.\n (5) Recovery of erroneous refund.--An erroneous refund shall be\nconsidered an underpayment of tax on the date made, and an assessment of\na deficiency arising out of an erroneous refund may be made at any time\nwithin two years from the making of the refund, except that the\nassessment may be made within five years from the making of the refund\nif it appears that any part of the refund was induced by fraud or\nmisrepresentation of a material fact.\n (6) Request for prompt assessment.--If a return is required for a\ndecedent or for his estate during the period of administration, the tax\nshall be assessed within eighteen months after written request therefor\n(made after the return is filed) by the executor, administrator or other\nperson representing the estate of such decedent, but not more than three\nyears after the return was filed, except as otherwise provided in this\nsubdivision and subdivision (d).\n (7) Report on u
is estate during the period of administration, the tax\nshall be assessed within eighteen months after written request therefor\n(made after the return is filed) by the executor, administrator or other\nperson representing the estate of such decedent, but not more than three\nyears after the return was filed, except as otherwise provided in this\nsubdivision and subdivision (d).\n (7) Report on use of certain property.--Under the circumstances\ndescribed in paragraph two of subdivision (g) of section twelve, the tax\nmay be assessed within three years after the filing of a return\nreporting that property has been used for purposes other than research\nand development to a greater extent than originally reported.\n (8) Report concerning waste treatment facility.--Under the\ncircumstances described in paragraph (3) of subdivision (h) of section\ntwelve, the tax may be assessed within three years after the filing of\nthe return containing the information required by such paragraph.\n (d) Omission of income on return.--The tax may be assessed at any time\nwithin six years after the return was filed if--\n (1) an individual omits from his city adjusted gross income an amount\nproperly includible therein which is in excess of twenty-five percentum\nof the amount of city adjusted gross income stated in the return, or\n (2) an estate or trust omits income from its return in an amount in\nexcess of twenty-five percentum of its income determined as if it were\nan individual computing his city adjusted gross income under section\ntwelve.\n For purposes of this subdivision there shall not be taken into account\nany amount which is omitted in the return if such amount is disclosed in\nthe return, or in a statement attached to the return, in a manner\nadequate to apprise the administrator of the nature and amount of such\nitem.\n (e) Suspension of running of period of limitation.--The running of the\nperiod of limitations on assessment or collection of tax or other amount\n(or of a transferee's liability) shall, after the mailing of a notice of\ndeficiency, be suspended for the period during which the administrator\nis prohibited under subdivision (c) of section sixty-one from making the\nassessment or from collecting by levy.\n