In 2016, the first wave of baby boomers turned 70½, and many more reach that milestone in 2017 and 2018. What’s so special about 70½? That’s the age when you must begin taking
required minimum distributions (RMD) from tax-deferred retirement accounts, including traditional IRAs, SIMPLE IRAs, SEP IRAs, SARSEPs, and 401(k), 403(b), and 457(b) plans. Original owners of Roth IRAs are not required to take RMDs.

If you’re still employed (and not a 5% owner), you may be able to delay minimum distributions from your current employer’s plan until after you retire, but you still must take RMDs from other tax-deferred accounts (except Roth IRAs). The RMD is the smallest amount you must withdraw each year, but you can always take more than the minimum amount.

Failure to take the appropriate RMD can trigger a 50% penalty on the amount that should have been withdrawn — one of the most severe penalties in the U.S. tax code. Distribution deadlines

Even though you must take an RMD for the tax year in which you turn 70½, you have a one-time opportunity to wait until April 1 (not April 15) of the following year to take your first distribution. For example:

• If your 70th birthday was in May 2017, you turned 70½ in November and must take an RMD for 2017 no later than April 1, 2018.
• You must take your 2018 distribution by December 31, 2018, your 2019 distribution by December 31, 2019, and so on.

IRS tables

Annual RMDs are based on the account balances of all your traditional IRAs and employer plans as of December 31 of the previous year, your current age, and your life expectancy as defined in IRS tables.

Most people use the Uniform Lifetime Table (Table III). If your spouse is more than 10 years younger than you and the sole beneficiary of your IRA, you must use the Joint Life and Last Survivor Expectancy Table (Table II). Table I is for account beneficiaries, who have different RMD requirements than original account owners. To calculate your RMD, divide the  value of each retirement account balance as of December 31 of the previous year by the distribution period in the IRS table.

Aggregating accounts

If you own multiple IRAs (traditional, SEP, or SIMPLE), you must calculate your RMD separately for each IRA, but you can actually withdraw the required amount from any of your accounts. For example, if you own two traditional IRAs and the RMDs are $5,000 and $10,000, respectively, you can withdraw that $15,000 from either (or both) of your accounts. Similar rules apply if you participate in multiple 403(b) plans. You must calculate your RMD separately for each 403(b) account, but you can take the resulting amount (in whole or in part) from any of your 403(b) accounts. But RMDs from 401(k) and 457(b) accounts cannot be aggregated. They must be calculated for each individual plan and taken only from that plan. Also keep in mind that RMDs for one type of account can never be taken from a different type of account. So, for example, a 401(k) required distribution cannot be taken from an IRA. In addition, RMDs from different account owners may never be aggregated, so one spouse’s RMD cannot be taken from the other spouse’s account, even if they file a joint tax return. Similarly, RMDs from an inherited retirement account may never be taken from accounts you personally own.

Birthday Guide: This chart provides sample RMD deadlines for older baby boomers.