Did you turn 70 1/2 last year? Make sure you tap your IRA before April 1.

Are you an IRA owner who turned 70 1/2 last year? If you haven't already started tapping your traditional IRA, then April 15 isn't the only IRS deadline you need to heed this year. You're also required to take your first minimum withdrawal no later than April 1. That's right, April Fool's Day. But this is no joke.

The tax law states that you must start taking mandatory payouts from traditional IRAs (but not from Roths) no later than April 1 of the year after the year you turn 70 1/2. So if you turned 70 1/2 in 2004, the deadline is less than two weeks away. Of course this also means you get stuck with the resulting income-tax bills. (The whole idea here is to make people who would otherwise leave their IRAs untouched to start taking taxable withdrawals.) And if you fail to take at least the minimum withdrawal amount by April 1, the IRS can sock you with a penalty equal to 50% of the shortfall. So this little rule isn't something you can afford to ignore.

Now, if you already took IRA withdrawals last year that equaled or exceeded the amount of your initial required minimum withdrawal, then you're blissfully unaffected by the April 1 deadline. Instead, you simply must take your next withdrawal by the end of the year.

But if you didn't take a withdrawal last year, then here's what you need to do. Use a joint life-expectancy figure (generally based on your age and someone 10 years your junior) to calculate your initial required minimum withdrawal. (Even those who don't have a designated beneficiary use the joint-life-expectancy figure.) The only time this joint-life-expectancy figure is not used is when the beneficiary is a spouse who's more than 10 years younger than you. (Click here for more on calculating minimum IRA withdrawals.) And don't forget: By Dec. 31 of this year, you must also take your second required minimum withdrawal.

Keep in mind that the IRA minimum-withdrawal rules also apply to simplified employee pension (SEP) accounts and Simple IRAs because they're also considered traditional IRAs for this purpose. Roth IRAs, on the other hand, are exempt from the minimum-withdrawal rules as long as the original account owner is alive.