The IRS requires all qualified account holders to withdraw a minimum amount from their tax-advantaged retirement accounts each year. This mandatory withdrawal is known as Required Minimum Distribution, or RMD.
IRA RMD rules apply to traditional IRA accounts only. One difference between traditional IRAs and Roth IRAs is that Roths do not have RMD provisions. This is because the contributions made to a Roth IRA have already been taxed. The government no longer has any interest in the monies inside of Roth IRAs because withdrawals from Roth IRAs are tax-free.
However, the IRS does want to be able to tax the value inside of traditional IRAs, which have often been funded either with pre-tax contributions, or by tax-deductible contributions. Either way, the IRS doesn’t want taxpayers to pass on their IRA accounts untaxed, and so requires that distributions from traditional IRA accounts and 401k accounts be made each year after the taxpayer turns 70 ½ years old.