All motions on actions already assigned to a Justice must be filed at least five business days before the return date. 1. Fill out a child support modification petition. 2.File the petition with the Family Court that most recently established your order. 3. For the motion, you need to file an affidavit of service reflecting service of the motion papers. A custodial parent may file a petition with their local child support agency. This online program from Family Legal Care guides you through filling out an Affidavit in Support. Intheblanks form required for any matter originating and electronically filed in Supreme or Surrogate's Courts in Richmond County. Bronx County Local Rules Regarding Motion Procedure. Related Statutory Provisions. To begin a child support case for children who live in the Bronx and are NOT on public assistance, go to the Support Collection Unit (SCU) on the 1st floor.