The IRS pays attention to postmarks. Don't let the fact that the IRS is dealing with millions of returns fool you. They'll notice if it has an April 16 postmark or later, IRS spokesman Mark Green said. Penalty assessments are based on the amount of tax liability.
The late filing penalty is 10 times greater than the late payment penalty. The late filing penalty is 5 percent per month (up to 25 percent) of the tax due. The late payment penalty is 0.5 percent per month.
DON'T OWE? DON'T WORRY
Those expecting a refund don't need to fill out an extension to file their tax return late, Mr. Green said, though filing a 4868 is a good measure in case you owe taxes.
If you filed an extension, it delays your filing deadline to Oct. 15. However, your extension was not an extension to pay. You still need to send in at least 90 percent of the estimated taxes you owe with the form.