§ 451. Continuing jurisdiction. 1. Except as provided in article
five-B of this act, the court has continuing jurisdiction over any
support proceeding brought under this article until its judgment is
completely satisfied and may modify, set aside or vacate any order
issued in the course of the proceeding, provided, however, that the
modification, set aside or vacatur shall not reduce or annul child
support arrears accrued prior to the making of an application pursuant
to this section. The court shall not reduce or annul any other arrears
unless the defaulting party shows good cause for failure to make
application for relief from the judgment or order directing payment
prior to the accrual of the arrears, in which case the facts and
circumstances constituting such good cause shall be set forth in a
written memorandum of decision. A modification may increase support
payments nunc pro tunc as of the date of the initial application for
support based on newly discovered evidence. Any retroactive amount of
support due shall be paid and be enforceable as provided in section four
hundred forty of this article. Upon an application to set aside or
vacate an order of support, no hearing shall be required unless such
application shall be supported by affidavit and other evidentiary
material sufficient to establish a prima facie case for the relief
requested.

2. A proceeding to modify an order of support shall be commenced by
the filing of a petition which shall allege facts sufficient to meet one
or more of the grounds enumerated in subdivision three of this section.

3. (a) The court may modify an order of child support, including an
order incorporating without merging an agreement or stipulation of the
parties, upon a showing of a substantial change in circumstances.
Incarceration shall not be considered voluntary unemployment and shall
not be a bar to finding a substantial change in circumstances.

(b) In addition, unless the parties have specifically opted out of the
following provisions in a validly executed agreement or stipulation
entered into between the parties, the court may modify an order of child
support where:

(i) three years have passed since the order was entered, last modified
or adjusted; or

(ii) there has been a change in either party's gross income by fifteen
percent or more since the order was entered, last modified, or adjusted.
A reduction in income shall not be considered as a ground for
modification unless it was involuntary and the party has made diligent
attempts to secure employment commensurate with his or her education,
ability, and experience.