Forbes:  In 2010 Max R. Levchin, chairman of social review site Yelp, sold 3.1 million shares of Yelp held in his Roth individual retirement account. Most of the $10.1 million he received was profit. But Levchin, a 36-year-old serial entrepreneur who started PayPal with ­billionaire Peter Thiel in 1998, won’t ever have to pay a penny of income tax on those gains. That’s because all earnings in a Roth IRA are tax free so long as its owner waits until age 59 1/2 to take money out.

Moreover, Securities & Exchange Commission filings show Levchin still has 3.9 million shares of Yelp, now trading near $22, in his Roth. So it appears his tax-free “retirement” kitty is worth at least $95 million—and maybe a lot more. We don’t know, for example, if Levchin’s Roth owned stock in social app company Slide, which he started in 2004 and sold to Google for $182 million in 2010. If Levchin doesn’t spend his mega-Roth in retirement, he can leave it to his kids or grandkids, who can, under current law, stretch out income-tax-free growth and withdrawals for decades.

Continue reading how billionaires avoid taxes.