Social Security & Medicare

than he likely has from his parents.

The problem with dropping a dime on his dad is that the wife will also likely be charged and that will mean even more children will be out there needing a home. Lousy parents might be better than no parents.

About all you can do is tell sonny boy you won't be helping him steal from the taxpayers, period, and that you want no part of any of his scams. Tell him if the state checks the address he's given, then he'll go to prison and you won't help him stay out, so he'd better update the kid's address now and forgo theft in his name.

ETA: I doubt you can be charged as an accessory to fraud since the false address is being reported by your stepson and not you. Ditto Federal taxes. Stepson is likely to find himself in a world of hurt.