Until 2005, tax filing extensions were only four months long. To request an extension of time to file your tax return, you will need to submit IRS Form 4868. You can find the form on the IRS' Web site as well as at many local post offices or office supply stores. The form can be submitted by mail, phone, or computer. But remember, an extension of time to file means just that—you have six extra months to get your paperwork filed. It is not an extension of time to pay the taxes you owe, if any. You generally will need to pay some or all of the estimated taxes due at the time you file your request for extension.