 Have you saved enough money to retire? Try a Roth IRA. A retirement account designed for the middle class is now also a tax-free piggy bank for some of the wealthiest Americans. How? Turning a Roth IRA into a giant tax shelter. First, here's how a Roth works. You invest a limited amount of money each year, and once the money is in the account, it's never taxed again, as long as you don't withdraw it before age 59 and a half. There used to be income limits on who could get one, but since 2010, there's been a backdoor for the rich. Pay a one-time tax, and you can turn a traditional retirement account worth millions into a Roth. Some others use investment tricks to grow a massive Roth. Step one, create your account. One Roth IRA, please. That was easy. Step two, invest. Use money in the Roth to buy low-value shares of a private company before it gets big. Some founders of startups buy shares in their own companies, with dirt-cheap prices set by the companies themselves. Step three, sell. As the value increases, sell some shares and keep the profits in your Roth IRA. Then reinvest the money pretty much however you want. Step four, wait patiently, and at age 59 and a half, you can begin to withdraw funds tax-free. Here's an example. In 1999, before he became a billionaire, PayPal founder Peter Thiel had a Roth IRA worth less than $2,000. 20 years later, his Roth had grown to more than $5 billion, the biggest account we found. He won't have to pay tax on a penny of that, and he can start to collect tax-free six years from now. Meanwhile, as of 2019, one in four working-age Americans had nothing saved for retirement, and many may never have enough money to retire at all.