Best Answer: If you e-file, you have until April 17th, 11:59pm to submit it (though if you wait that long and have computer difficulties, the IRS isn't going to forgive you). If you mail, you have until midnight tonight to file.
The consequences differ depending on whether you owe the IRS money or the IRS owes you a refund.
If You Are Getting a Refund
This is one of the great little secrets about the tax law. If you have a refund coming — as more than two-thirds of taxpayers do every year — then there is no penalty for failing to file your tax return by the deadline, even if you don't ask for an extension.
That's not to say there aren't darned good reasons for
filing on time, though, even if you have a refund coming:
You can't get your money back until you file, so you should file as soon as you can to get your money as soon as possible.
If you are eligible for a government rebate (stimulus payment) as a result of the 2008 Economic Stimulus Plan, you can't receive it until you file your 2007 return.
The statute of limitations for the IRS to audit your return starts at the later of the original due date or when you actually file your return. So, the sooner you file, the sooner the clock starts ticking.
Some rather arcane elections must be made by the due date, even if you have a refund coming. This applies to a very tiny percentage of taxpayers.