N.Y. FCT Law § 451

§ 451. Continuing jurisdiction. 1. Except as provided in article\nfive-B of this act, the court has continuing jurisdiction over any\nsupport proceeding brought under this article until its judgment is\ncompletely satisfied and may modify, set aside or vacate any order\nissued in the course of the proceeding, provided, however, that the\nmodification, set aside or vacatur shall not reduce or annul child\nsupport arrears accrued prior to the making of an application pursuant\nto this section. The court shall not reduce or annul any other arrears\nunless the defaulting party shows good cause for failure to make\napplication for relief from the judgment or order directing payment\nprior to the accrual of the arrears, in which case the facts and\ncircumstances constituting such good cause shall be set forth in a\nwritten memorandum of decision. A modification may increase support\npayments nunc pro tunc as of the date of the initial application for\nsupport based on newly discovered evidence. Any retroactive amount of\nsupport due shall be paid and be enforceable as provided in section four\nhundred forty of this article. Upon an application to set aside or\nvacate an order of support, no hearing shall be required unless such\napplication shall be supported by affidavit and other evidentiary\nmaterial sufficient to establish a prima facie case for the relief\nrequested.\n 2. A proceeding to modify an order of support shall be commenced by\nthe filing of a petition which shall allege facts sufficient to meet one\nor more of the grounds enumerated in subdivision three of this section.\n 3. (a) The court may modify an order of child support, including an\norder incorporating without merging an agreement or stipulation of the\nparties, upon a showing of a substantial change in circumstances.\nIncarceration shall not be considered voluntary unemployment and shall\nnot be a bar to finding a substantial change in circumstances.\n (b) In addition, unless the parties have specifically opted out of the\nfollowing provisions in a validly executed agreement or stipulation\nentered into between the parties, the court may modify an order of child\nsupport where:\n (i) three years have passed since the order was entered, last modified\nor adjusted; or\n (ii) there has been a change in either party's gross income by fifteen\npercent or more since the order was entered, last modified, or adjusted.\nA reduction in income shall not be considered as a ground for\nmodification unless it was involuntary and the party has made diligent\nattempts to secure employment commensurate with his or her education,\nability, and experience.\n