Arrears and Child Support Emancipation

Hello! I received a child support emancipation notice months ago advising me that my case will cease next month when my son turns 18. He is currently not in school. My question is will I still be obligated to pay the Arrears. If the answer is Yes is there anything I can do to get this reduced expunged, etc. The arrears covers two years before the court order was established. I have been compliant for 9 years now. In addition, a small amount of each payment goes supposedly has gone to the arrears for the past 9 years. Any information is greatly appreciated.