While you can file for a six-month extension using Form 4868, you still need to file that form and pay any tax you owe by the regular filing deadline.

Really, it's much better to get it all over with and not end up paying more to the IRS than you need to.

Signing tax form, taxes, signature, money

No. 1: Forgetting to sign your return

Don't make perhaps the most embarrassing tax mistake of all -- sign your return.

According to the IRS, 1 million people each year forget to take that one final, simple step.

If you're filing electronically, you obviously don't have to worry about this step. Besides the fact there are no physical papers to actually sign, tax preparation software and websites won't send your return to the IRS without every step being complete.

But, believe it or not, about half the people filing individual tax returns still do so the old fashioned way. So if you're one of those filers rushing to the post office at the last minute, don't forget to sign your forms before stuffing them into the envelope.

Not signing your forms -- or forgetting to have your spouse sign if filing jointly -- won't kill your return, but it could put your last-minute filing past the deadline and will delay any return you have coming.