Haven't filed your taxes yet? No rush.

NEW YORK (CNNMoney.com) -- Scrambling to file your taxes before the April 15 deadline? Relax. There's a good chance it won't cost you a penny to submit your return late.

Many people fear that a tardy return will involve penalties, headaches or even jail time. But the reality is that if you are one of the majority of Americans owed a refund this year, the Internal Revenue Service can't touch you. And in some rare cases, the IRS might even owe you more money.

But if you aren't getting a refund and need to pony up, there could be major consequences for not getting your return in on time. The penalty for filing a late tax return is 5% interest on the amount owed for each month that you fail to file, up to a maximum of 25%.

"As long as [you're] sure that there is no tax due on the return, I would definitely advise taxpayers not to get too worked up over meeting the April 15 deadline," said Robert Willens, a professor of taxation at Columbia Business School and president of a tax consulting firm.

Almost 90% of returns processed so far have resulted in a refund averaging $3,036. And since the vast majority of filers are due refunds, most people have no need to rush to make the deadline.

The IRS also pays interest on refunds that have been delayed more than 45 days because of slow processing. So if your refund doesn't make it to you on time, you could actually wind up getting extra money back, regardless of whether you missed the April 15 deadline.

But for the extremely tardy filers, be careful: there is a statute of limitations on refunds. If you wait more than 3 years, the IRS is no longer required to pay you.

If you're not sure that a refund is coming your way, it may be smarter to play it safe and either file on time or file an extension. You can get an automatic tax extension simply by submitting Form 4868 to the IRS, which will move the filing deadline from April 15 to Oct. 15.

While a late filer who's owed a refund faces no consequences with or without an extension, those who are unsure about their tax bill could find themselves in trouble.

"It's better to be safe than sorry, so even if you think you're going to get a refund, file [Form 4868] anyway because it will protect you," said Robert Kerr, senior director of government relations at the National Association of Enrolled Agents.

"If you finalize your [late] return only to discover that the refund you expected has turned into a hefty balance due ... you're going to find yourself up that famous creek without a paddle," he added.

If you've already filed, but you still haven't received your refund, you can use the IRS's "Refund Status" tool on its Web site or call the IRS Refund Hotline at 800--829-1954.

Where the late filers are: The biggest procrastinators are taxpayers in Houston, who top the list of late filers, according to a tally from TurboTax based on the number of returns filed through its online service between April 14 and 17 of last year.

Chicago was the second tardiest city, while New York City came in third.

Austin, Texas, San Francisco and Seattle ranked fourth, fifth and sixth place, respectively, while San Diego, Los Angeles, Dallas and Las Vegas finished up the "top ten" list of late filers.