Editor's Note: This article is part of our 2013 Tax Tips series. Robert Flach is an expert with almost 40 years of experience as a tax professional and also blogs as The Wandering Tax Pro. NEW YORK ( MainStreet) --Happy Tax Day! Today is the deadline for filing your 2012 federal and state income tax returns. The envelopes must be postmarked by midnight tonight!See also: What Are Your Biggest Tax Worres? But if you haven't prepared your return yet, don't worry - all is not lost. You can file a Form 4868 to request a six-month extension, until October 15, 2013, to file the return. The Form 4868 also must be postmarked by midnight tonight. In many cases filing a federal extension request will also extend your state return. You can download Form 4868 at the IRS website. I must point out that the extension is for time to file your tax - it is not an extension of time to pay your tax. Uncle Sam will charge interest, and a small penalty, from April 16 until your tax is paid in full. If you think you will owe the IRS, you should include a check with the Form 4868. And if you think you will owe state tax you should file a state extension form with a check. See also:9 Last Minute Tax Tips But what if you don't have the money to pay the taxes you owe? It is very important that you get your tax return, or extension request, in the mail today - even if you can't pay all, or any, of the tax due. Send what you can with the return or extension - but if you can't send anything, you still must be sure to mail the return or extension! The penalty for paying late is 0.5% of the tax due per month, or part thereof, until paid. The penalty for filing late is 5% per month - 10 times as much!