These forms and instructions are available in the General Clerk's Office, Room 108, in the Nassau County. Child support and spousal support are handled in Family Court.We offer 150 years of combined experience and a background in banking and finance to give clients a competitive advantage for spousal support or alimony cases. Generally, courts will determine a date at which alimony payments will cease. Contact Us For a Consultation. Are you seeking reliable legal guidance for your child support matters in Nassau County? It is common for both spouses to create a joint agreement that determines how much spousal support each party receives. Fill out a child support modification petition. 2. File the petition with the Family Court that most recently established your order. 3. These payments must be made until the child reaches 21 years of age.