The year after an investor reaches age 70½, he/she is required to withdraw a minimum amount of money from tax-advantaged retirement accounts. This required minimum distribution (or RMD) is required in subsequent years as well.
Investors are required to take RMDs from the following accounts: 401(k) plans, 403(b) plans, certain 457(b) plans, IRAs.
RMDs are waived for 2009 under the Worker, Retiree, and Employer Recovery Act of 2008, which the President signed on December 23, 2008. Any investors who took a withdrawal in 2009 may be able to roll the withdrawn amount into another retirement plan. The IRS Notice 2009-9 has more details.
If you don't need to withdraw funds this year you have the opportunity to keep funds tax deferred.