Legal Question in Family Law in Washington

To start, usually when I run into this situation, it's almost always impossible to do anything. That said, your best bet is to bring a motion to re-open the judgment, on the basis of lack of service. You will need to show that you were never served. Look into the case records held by the Court clerk and see if there is a return of service, or declaration or service, or proof of service (I've seen it called many things in Washington) on file for you, for the hearing or petition or motion that awarded your ex this $5,000 for back support.

If it is there, you are going to have to demonstrate that it is either inaccurate, does not comply with the statute, or was fraudulent, in that the server lies about serving you. The burden lies with you to prove any of the above (faulty, fraudulent, etc.). It is a very tough burden to meet.

Beyond that, you'll want to check out the statutes of limitation on this issue. It is tolled (meaning we halt the clock) until you knew, or should have known about the judgment. It sounds like you've known about it for some time. If you're beyond the statute, then you have no way to reopen and get the judgment set aside.