t's April 15th and you're starting to sweat. Your tax return is due today and your accountant won't answer your calls. Not that it would do you much good, anyway. You're still waiting for a K-1 form from that partnership you were persuaded to invest in. And yesterday you got an amended 1099 from your bank correcting the amount of interest that was reported in February.

Regardless, the return is due now and there are penalties for late filing. The Internal Revenue Service can hit you with a late filing penalty of 5 percent of the tax not paid by the due date for each month or part of a month your return is late. Generally, the maximum penalty is 25 percent. But if your return is more than 60 days late, the minimum penalty is $100 or the balance of the tax due on your return, whichever is smaller.

On top of the late filing penalty, there is a late payment penalty. This is usually 0.5 percent of any tax not paid by the due date. It is charged for part of a month that the tax is unpaid. The maximum penalty is 25 percent.

The late payment penalty can be excused if you have and can show "reasonable cause" for not paying on time. You are considered to have reasonable cause if at least 90 percent of your actual liability is paid before the regular due date of your return through withholding or estimated tax payments.

However, you'll owe interest on any tax not paid by the due date of your return. This interest runs until you pay the tax. Even if you have a good reason for not paying on time, you'll still owe the interest.

The IRS has a simple form that allows you an automatic four-month extension to file your taxes. It's Form 4868, and it's easy to complete, even without an accountant. All the form asks is your name, address and Social Security number. It asks you to estimate your tax liability and send any balance due. If you make this payment and hit at least 90 percent of your real liability, you win. You don't pay a late filing or late payment penalty.

You can get this form at any IRS office or order it toll free at 1-800-TAX-FORM (1-800-829-3676). You must file it by the regular due date of your return, usually April 15. It is an automatic extension. You don't have to give the IRS any reason. You can get it even if the only reason you haven't filed is you were lazy or didn't want to think about it.

Form 4868 gives you another four months to complete and send in your return. If you're still not ready, all is not lost.

You can get a second extension by filing Form 2688 before the first extension expires. This extension gives you another two months, until Oct. 15, to file your return.

But here you must provide a reason for the request. For example, waiting for missing records such as a late 1099, or if your accountant has become ill or has died, have all been acceptable reasons. Any "reasonable" explanation should be OK. (Don't try "my dog ate my W-2.") Even if your request for an extension is denied, the IRS usually will allow you five to 10 days from the date of denial to get your return in. The IRS has been very "consumer friendly" in this area.

Remember, however, that these extensions only extend the date for filing, not for paying. If you don't pay the amount due by the due date, you'll owe interest and, potentially, a penalty for late payment. So even if your return isn't complete, estimate the taxes due and send in any balance with Form 4868. Don't think that the automatic extension for filing also extends the date for paying. It doesn't work that way and lots of people get caught.

So how are you going to estimate how much you owe? The best way would be to use Decision Center's tax estimator, which will give you a solid ballpark figure of what you owe.

In the past, if you didn't estimate and send a sufficient payment with the request for an extension, you could be denied even the automatic four-month extension for filing. That's no longer the rule. If you file the Form 4868, even if you don't send in the payment of the tax you estimate as due, you still qualify for the extension and avoid those failure to file penalties.

You should also be aware that the statute of limitations runs from the date you actually file, not the original due date. The statute of limitations is a law that limits the amount of time the IRS has to audit your return. Normally, that is three years from the due date of the return - usually April 15.

If the IRS doesn't audit you within that three-year period, the government is legally prohibited from challenging your deductions. (If the IRS can prove you committed fraud, all bets are off. Here the burden of proof is on the IRS. They must prove that you intended to cheat - a difficult burden.) If you file an extension, the statute of limitations doesn't begin until the return is actually filed.

If you're a U.S. citizen or resident and were out of the country, you automatically get a two-month extension to file your return. "Out of the country' means either:

By filing the Form 4868, you get an additional two months (for a total of four) to file your return.

Always file Form 4868 before Form 2688. Only in cases of undue hardship will the IRS approve your request for an additional extension without receiving Form 4868 first.

Getting an extension to file is easy - as long as you know what to do.