In NY do I still owe child support if the child is 18 and just quit high school.

Probably not. What does the child support order actually say?

There isn't a legal court order for us to pay child support, we just do. But I wondered if we had a fight against it if the mother let her quit school and let her stay wherever she wants. The only court order is joint custody and legal address with the mother.

NewYork usually runs child support until age 21. But that is under court order. Now that the child is an adult then other party may or may not bring it before the courts at this time. We can't predict what a judge will do.