One of the tax systems in the US is for wage earners. The government takes money from them out of each paycheck - so it knows how much they make, and those workers can't cheat to any significant degree. But the other tax system is for capital. Those with capital get to tell the government what they want to tell. They may get audited, but if their tax returns are of any size the government doesn't have enough of the smart auditors to figure out what's really going on. And there are the rules that allow you to do things like take in money today and pay taxes on it thirty years from now.