It depends on your state and your obligation. For one, not all states have laws ending support (emancipating the child) at 18. Many go through the 18th year and/or graduation from high school, which every is later. And, if the child goes on to higher education, support may continue. You need to check what the law is in your state. And, your order may have specifics that would require a lawyer. First, find out what the emancipation laws are in your state, then check your state's child support office - call or website - for details on how to go about the process. The basic answer is no, you do not need an attorney ... but there are exceptions.
30+ years in the child support enforcement business