What state are you in? Poster above is correct, your state should have a support enforcement office and/or a way to contact someone at the child support division - ask if they have a credit reporting division. I would simply write a nice letter to the above and state that an outstanding balance appears on your credit reports and you'd like to know if it is correct, what it is for and how/where you should direct any payment due.
Your remaining balance could simply be past interest, court costs, administration fees, bill for genetic testing, etc. None of the above would be paid for through your employer withholding as that is a court order for _only_ the monthly amount due. Sometimes half the monthly due per pay period depending on the frequency
Depending on your state, once you get completely caught up for an good length of time, you can again write to the above office asking if they will remove the CS account from your credit reports. I'm in Texas and was hit with a huge sum at once that became a judgment around 6 months afterwards simply because I could not pay off the total amount quickly enough. Not to worry. The account has been either remove completely or had all late payment remarks removed after I was finally caught up for a while.
