Taxation is not an issue of morality. Lawmakers come and go, and yesterday's just law is today's heinous crime. And so it goes... It's a case of practicality. If we pay our dues, we get a certain return (police, roads, a military etc). Those who have power use that power to enforce their will on those who do not have power. If we as individuals agree with the moral position of those with power, we call them good leaders and we call their laws good laws, and vice versa. Law (man's law) is the exercise of power, nothing more. But whether we agree or not, we should still be mindful that there are those with more (vastly more) power than us. The mouse may despise the cat, but it should be wise and respect the cat's power, if it wants to live an easy life. There are risks and rewards in defying the law. Sometimes the rewards are meh, and the risk is meh. The IRS, like all tax collectors, can perform a "lifestyle audit" and see if your declared earnings tally with your lifestyle. Obviously, if there is a modest undeclared income stream then it's probably going to go unnoticed. If it's a case of a Lamborghini parked outside your trailer home, then it's going to be noticed. It's a matter of proportion. Sometimes we may want to spend undeclared money and *if* there was a lifestyle audit, they would want to know where that money came from. Why did you buy a new boat engine when your finances put you at close to the poverty line, etc? You could probably talk your way out of this, but is it worth the stress? Again, depends how much money we are talking about. If it's an amount that could reasonably be diluted in your declared income-outgoing, then it's nothing to worry about.