Get a paternity test. If you do not believe that you are the biological father of the child to whom you owe back child support, go to your local child support enforcement office and request a paternity test. If the paternity test results confirm that you are not the father, request a hearing and ask the judge to nullify your obligation to back child support payments.
Get evidence of your inability to pay. If you cannot fulfill your child support obligations due to a long-term medical condition, job loss, or other severe financial hardship, get written evidence describing your situation and present it to the family court judge. Although you may not be able to have your entire child support obligations erased, the judge may be able to come up with a payment arrangement that will not cause you undue hardship.
Talk to a lawyer and challenge the decision. If you believe that the court has erred in requesting back child support payments, seek the assistance of a lawyer. Keep in mind that it is not common for courts to reverse orders for child support unless there were errors in the facts presented at the initial hearing.