American tax forms have an "other income" field. That's where you can report any money you've made not covered by the other fields including any ill gotten gains. That section doesn't require you to list a source, and even if it did nobody expects you to list "$7,800 - meth sales, $32,200 - crack sales, $50,000 - robberies". You'd just say "Other income - $90,000"
The logic being that if the government never gives you the opportunity to pay taxes on something, then they can't charge you with tax evasion. Plus there's a lot of money in crime! If the US can get a piece of that pie they will!
Finally, the IRS is an already underfunded organization and contrary to the popular narrative, is very easy to work with. If you make a genuine good faith effort to pay your taxes and they find issues, an agent will work with you to resolve it. They'll set up payment plans, defer payments, and more if you're cooperative. All this is to say that reporting people for crimes besides tax ones and terrorism (the only one they're legally required to report to outside agencies) just makes their job harder, so they don't