Withdrawal exceptions
The IRS does allow a few instances where you don't have to touch your retirement money just yet.

First, if all your retirement savings are in a Roth IRA, you're exempt from this rule. Earnings in Roth accounts are tax-free, and you can leave your money in there as long as you like.

Second, if you are still working, you can wait until you actually retire before you collect from your company pension or 401(k), "as long as you're not more than 5 percent owner of that company," says Ed Slott, author of "Parlay Your IRA into a Family Fortune." But if you have other, nonwork-related accounts, such as an IRA other than a Roth, you've got to start taking money from them now.

Third, if you've already withdrawn the minimum required amount, either last year when you actually celebrated your 70th-and-a-half birthday or earlier this year, you don't have to worry about the April 1 deadline. But you will have to take another chunk out of your IRA before the year's end. The first amount you withdrew counts toward the year when you actually reached the milestone age. The second one applies to this year's required distribution.

And even if you've been tapping retirement accounts before you became a septuagenarian, now you've got to keep a close eye on exactly how much you take out. All subsequent withdrawals must meet the IRS mandatory amounts.

Other withdrawal rules
You can always take out more than the required amount. But that won't affect distributions in future years. Say, for example, your required withdrawal this year is $1,500, but you take out $2,000. You can't carry that $500 over to count against the next required distribution. But, because you've reduced your IRA balance, your subsequent minimum distributions will be lowered.

Do you have multiple retirement accounts? Then you must calculate the minimum withdrawal amount for each, but you don't necessarily have to raid them all. You can add the separate amounts and take the total from just one.

If you made any nondeductible contributions to your traditional IRA, make sure you have the paperwork to back that up. This is part of the reason why you need to file Form 8606, which tracks these amounts and establishes your cost basis in your account. Your nondeductible contributions are not taxed when you withdraw them. Rather, they are a return of your investment (i.e., your cost basis) in your IRA.

And the IRS will let you take your required distribution in installments. Just make sure that these disbursements, be they monthly, quarterly or some other increment, total at least the yearly minimum amount you're obligated to withdraw.

You can get more information on required minimum distributions in both IRS Publication 575, Pension and Annuity Income, and IRS Publication 590, Individual Retirement Arrangements. The various life expectancy tables to use in computing withdrawals can be found in Appendix C of Publication 590.