There is no doubt that many people who are paid in cash under report their income. At least in the case of servers, however, the IRS has a pretty good idea how

There is no doubt that many people who are paid in cash under report their income. At least in the case of servers, however, the IRS has a pretty good idea how much you are getting in tips. If you don't report enough, you will be audited and you will get a bill. I'm acquainted with someone who tried this and he was still paying off his tax bill a couple of decades later.