The child for whom I pay child support turns 18 in January. How do I terminate the support order?

Child support should be terminated by an order of the court. If DOR is involved, then they will want a court order, otherwise they may seek an enforcement action. You can bring the action yourself, and if you plan to do that there are some resources on the internet and some of the courts have Attorney-of-day Programs to offer some information.

Also, consider having an attorney review the separation agreement and any orders related to the child support and assisting your through the process. I handle these types of matters.

DISCLAIMER: This answer is provided in response to a "hypothetical" question and provided for general, informational purposes and does not create an attorney/client relationship. The information presented is not legal advice and may change based additional information and research. It is recommended that you speak to an attorney to discuss your specific legal issues.

Termination is not only age alone. If the child attends full-time school, support should continue.