You might have been just a toddler when a half-year mattered to your age, but if you’re an owner of an Individual Retirement Account, you need to be mindful of when you turn 7012.

If you’ve stopped working, you’ve likely rolled over the assets from your employer’s 401(k) into your own IRA. This transition gave you more choices and more control over your investments.

But once you reach age 7012, the government says you must start withdrawing money from your IRA and pay federal income tax on that amount whether you need the money or not. If you fail to do so, the government can assess a 50% penalty on the amount you should have withdrawn.

For savers who have diligently put money aside in an IRA, that’s a tough concept to grasp. “The reason it’s challenging is that it’s a shift,” says Ed Slott, an expert on IRAs who has authored books on the subject and educates financial planners. “You’re going in one direction your whole life. Then you have to stop and go the other way even if you don’t want to.”

If you’re a caregiver for someone nearing age 7012, now’s a good time to get familiar with the rules for required minimum distributions (RMDs) from IRAs. For the sake of simplicity, we’ll stick to the rules for traditional IRAs in this article.

What Are Required Minimum Distributions?

You cannot keep retirement funds in your traditional IRA account forever because Uncle Sam wants to start collecting taxes on the money you’ve saved. You generally have to start taking withdrawals the year you reach age 7012 and include them as part of your income on your tax return.

And in a one-time-only twist, you have until April 1 of the year after you turn 7012 to take your first distribution. In subsequent years, you must take your annual distribution by December 31 of each calendar year.

If you get tripped up by the age requirement, you’re not alone. “The age thing really throws people,” says Slott. “That confuses the heck out of most people.”

An example may help lift the fog: The IRS says you turn 7012 six calendar months after your birthday. For example, if your 70th birthday fell on June 30, 2016, you turn 7012 on Dec. 30, 2016. So you must take your first distribution from your IRA by April 1, 2017.

If your birthday was July 1, 2016, you turn 7012 on Jan. 1, 2017, so you don’t have to take your first distribution until April 1, 2018. But remember, you’ll likely take two distributions in 2018: the one for 2017 from the year you turned 7012 and another by Dec. 31 for calendar year 2018.

Consider taking your first-year distribution by December 31, because if you wait until the following April 1 you’ll be taking two distributions in one year and that may vault you into a higher tax bracket.

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How Much Should I Withdraw?

Once you’ve figured the age requirement for distributions, more mental gymnastics await.

The required minimum distribution for any year is the account balance at the end of the immediately preceding calendar year divided by a distribution period from the IRS Uniform Lifetime Table. (You can find this table in IRS Publication 590-B).

For example, if you reached 7012 in 2015, you were required to make your first withdrawal by April 1, 2016, based on the IRA account balance as of Dec. 31, 2014. If the balance was $100,000, then using the Uniform Lifetime table you divide that balance by the factor in the table (in this case, 27.4) to determine that the first required distribution was $3,649.64.

Special rules apply to IRA owners whose sole beneficiary is a spouse more than 10 years younger, which permits owners to withdraw less money. In this instance, you use the Joint Life and Last Survivor Expectancy table, which you can also find in Publication 590-B.

In the same $100,000 IRA example, suppose you have a spouse who is 56 years old and is the sole beneficiary of your IRA. Using the Joint Life table, the factor is 30.3, so your required distribution would be $3,300.33.

Many people have more than one IRA. In that case, calculate the distributions you must take from each IRA and add them up. You can then take this total distribution from one or more IRAs. If you are a caregiver, consider consolidating multiple IRAs into one to simplify this process.

Of course, you don’t have to withdraw a required distribution in one lump sum. You may prefer to take monthly or quarterly distributions instead to spread it throughout the year.

If you and your spouse each have IRAs, you must calculate and each take distributions from your own IRAs even if you file a joint tax return. “The I in IRA stands for individual,” Slott says.

Ask for Help

If your head spins from figuring age and distribution requirements, consider getting help from a pro. Slott’s web site, IRA Help, provides a tool to help you search for one of 400 financial planners he has trained in depth on the intricacies of IRAs for retirees.

Slott also publishes helpful guides for consumers nearing or already in retirement. Consider ordering Slott’s Retirement Decisions Guide. He updates the material every year to reflect the latest tax changes, and it’s an easy read.

With the wave Baby Boomers retiring, many brokers and mutual fund companies have created online calculators that help IRA owners figure out required minimum distributions. For example, T. Rowe Price has a free online calculator and offers the RMDNavigator to its account holders to calculate and make their distributions automatically each year.

If you are financially savvy and want to double-check your calculations, the Financial Industry Regulatory Authority provides an online calculator for required minimum distributions. Note that this calculator can’t be used if your primary beneficiary is a spouse who is more than 10 years younger.

What About the Penalty?

The penalty for failing to take required distributions from an IRA is 50% excise tax on the amount not distributed as required. For example, if your required distribution is $3,000 and you failed to take it, you must pay a $1,500 penalty.

Fortunately, you can file IRS Form 5329 and request a waiver of the penalty. In the instructions, the IRS says it will waive all or part of this tax if any of the shortfall is due to reasonable error and you are taking steps to remedy the problem.

If you’re not sure how to fill out the Form 5329, consider hiring a tax accountant who can help you or the person you care for. The size of the penalty can make this decision well worth the expense. Your chances for leniency are good: “They waive it almost every time,” Slott says.