Under New Jersey law, a child typically becomes a legal adult ("emancipated") -- and child support automatically terminates -- when he or she turns 19 years old, marries or enters military service. A parent can also ask the court to end support for a child who lives on his or her own, is self-supporting, gainfully employed, etc.
For more information on emancipation, see Emancipation of a Child in New Jersey.
Support doesn't automatically terminate if a child is financially dependent on his or her parents because of a severe mental or physical incapacity, and the support obligation is specified in an existing court order or judgment. Support also doesn't automatically terminate if the child is in an out-of-home placement via the Division of Child Protection and Permanency in the Department of Children and Families.
Parents can agree on a different age or milestone to mark the end of support, and courts will enforce settlement agreements and/or judgments that clearly spell out each parent's obligation to contribute to costs beyond age 19. However, courts won't order or enforce child support beyond age 23 except where the child has a disability.
Where parents cannot agree, or one parent doesn't want to pay beyond age 19, a custodial parent can submit a "Request for Continuation of Support" form plus supporting documentation asking that support be continued. Courts will typically grant the order in cases where the child (1) is still enrolled in high school or a similar program, (2) is a full time college or post-secondary educational student, (3) was diagnosed by a government agency with a physical or mental disability that existed prior to reaching age 19 and which requires ongoing support, or (4) needs support because of "exceptional circumstances".