NEW YORK (CNN/Money) - If you're one of the 8.5 million taxpayers who filed for an extension on your 2003 tax return your time is nearly running out.

"August 16 is the extension due date for individual tax returns and that is based on the people who filed the automatic extension by April 15," said Bert DuMars, director of electronic tax administration for the IRS.

As with the April tax deadline, your return must be postmarked no later than midnight Monday.

Still not ready? If you can't make the August 16 date, you can file a Form 2688 which will allow you to extend to October 15. That form, however, must be filled out and sent to the IRS by the Monday deadline.

Approximately 3 million tax payers file for a second extension, so you won't be alone.

If you just can't pay your all of your taxes right now, try to pay at least a small amount as a show of good faith. You can also request to make your payments as part of an installment plan with the IRS Form 9456. The interest rate for this type of plan is 4 percent.

Don't think that you can get away with not paying. Haven't yet paid your tax bill and haven't filled out a tax return? Uncle Sam will assess a 5 percent per month penalty on the outstanding balance up to a quarter of the total amount due.

If you filed a tax return but didn't pay your taxes, you'll be assessed a 0.5 percent penalty for each month it is overdue plus interest.

If you're one of the 8.5 million taxpayers who filed for an extension on your tax return - your time is running out. August 16 is the extension due date. CNNfn's Valerie Morris reports. Play video (Real or Windows Media)

The IRS says the easiest way to meet Monday's extension deadline is to file online using e-file. E-file works with several different types of software and will guide you through the tax-filing process step-by-step. And the price is right: it's free.

Just go to IRS.gov, click on the free file section and find a list of participating vendors.

If you've been turned down for a second extension, you have 10 days from when you receive the notice from IRS to pay your taxes.