These forms and instructions are available in the General Clerk's Office, Room 108, in the Nassau County. 1. Fill out a child support modification petition. 2.File the petition with the Family Court that most recently established your order. 3. This Easy Form helps you ask the court to increase or decrease your current child support order. This is called child support modification. Qualified Medical Child Support Order. The forms below are some of the most common forms used in the Domestic Relations Division, but there are many more. The only way you can get a modification to a child support order is to prove a decrease in your income over the past year. Form: Petition for Modification of Child Support. First blank: Your name.