You're over age 71 1/2, with a designated beneficiary

Now let's assume you designated your spouse, who's five years younger, as your sole IRA beneficiary.

For instance, say you'll be 73 as of Dec. 31, 2012, and your spouse will be 68. Your IRA balance as of Dec. 31, 2011, was $250,000. Your 2011 minimum withdrawal equals $250,000 divided by the joint life-expectancy figure of 24.7 for someone 73 years old (from the calculator below). The answer is $10,121 ($250,000/24.7). You must withdraw that amount (at least) by Dec. 31, 2012.

Next year (2013) you must take another minimum withdrawal by Dec. 31, 2013. That amount will equal your Dec. 31, 2012, IRA balance divided by the joint life-expectancy figure based on your age at the end of next year.

What if My Spouse Is More Than 10 Years Younger Than I Am?

Good question. When your spouse is more than 10 years younger than you and is designated as the sole beneficiary of your IRA, a special set of favorable rules applies in calculating your 2012 minimum withdrawal.

Say you'll be 73 at the end of this year (2012) and your spouse will be 61 by that date. Under special rules, your 2011 minimum withdrawal equals $250,000 divided by your joint life-expectancy figure of 26.1 from Table II in Appendix C of IRS Publication 590 (Individual Retirement Arrangements). The answer is $9,579 ($250,000/26.1). You must take out at least that amount by Dec. 31, 2012.

Next year (2013) you must take another minimum withdrawal by Dec. 31, 2013. That amount will equal your Dec. 31, 2012 IRA balance divided by the joint life-expectancy figure, based on your age and your spouse's age at the end of next year, from Table II.

A Nonspouse Is Your Designated Beneficiary

If you've designated a nonspouse (such as a sibling, child, or grandchild) as your IRA beneficiary, the age of the beneficiary doesn't matter. Your 2012 minimum withdrawal calculation depends only on your age as of the end of this year and your IRA account balance as of the end of last year (Dec. 31, 2010).

For example, say you'll be 73 at the end of this year (2012) and that your IRA balance was $250,000 at the end of last year. Your 2012 minimum withdrawal equals $250,000 divided by the joint life-expectancy divisor of 24.7 for an IRA owner who is 73 years old (from the calculator below). The answer is $10,121 ($250,000/24.7). You must withdraw that amount (at least) by Dec. 31, 2012.

Next year (2013) you must take another minimum withdrawal by Dec. 31, 2013. That amount will equal your Dec. 31, 2012 IRA balance divided by the joint life-expectancy figure based on your age at the end of next year.