More than $1 billion is waiting for one million people. No, this isn't one of those crazy sweepstakes that try to scam you into putting money on an iTunes card to claim your prize.

We're talking about real money, not fake cash here.

The Internal Revenue Service says that its unclaimed federal income tax refunds total more than $1 billion. The refunds apply to an estimated one million taxpayers who did not file a federal tax return for 2013. The IRS figures are an estimate and reflect W-2 withholding information.

Experts note that when the actual returns are filed, the refunds could be more or less than what some filers would expect based on other income and deductions, filing status and exemptions.

The good news: It's still possible to claim some of this money. Half of the refunds are for more than $763, according to IRS data.

The bad news: You will need to file a federal income tax return for 2013 by this year's tax deadline of April 18. It will have to be a paper return — you cannot file this return electronically.

Current and prior year tax forms and instructions are available at www.IRS.gov. See the "Forms and Publications" page. Or you can call 800-829-3676.

“The clock is ticking down, and we want people to get their money. But if you don’t file and claim it, you’re not going to get it,” said Luis D. Garcia, an IRS spokesperson in Detroit.

If someone does not file a federal return within three years to claim a refund, the money becomes property of the U.S. Treasury.

In Michigan, the IRS estimates that 33,600 people are owed nearly $34 million in unclaimed federal income tax refunds for 2013. In Florida, about 66,900 people are owed nearly $67.8 million. In Ohio, about 36,000 people are owed about $34.5 million. In Indiana, about 21,700 people are owed nearly $22.1 million.

What's holding up people?

Too often, some taxpayers wrongly believe that if they missed the filing deadline for a given year, they'll get socked with a penalty — even if they are owed a refund. That's not true.

To be sure, you'd face penalties for filing late and paying late if you owed taxes and didn't file a return on time or seek an extension.

If you file your return more than 60 days after the due date or extended due date, the minimum penalty is the smaller of $205 or 100% of the unpaid tax. Otherwise, the penalty can be as much as 5% of your unpaid taxes each month up to a maximum of 25%.

On top of that, there's a penalty for a late payment. It is generally 0.5% of your unpaid taxes per month; it maxes out at 25% of your unpaid taxes.

Interest builds on the outstanding balance, too. (Experts advise that you request an extension during the tax season if you cannot make the April deadline to avoid at least that late filing penalty.)

If you're owed a refund, though, you're not going to be hit with penalties or interest.

"There's no penalty or disadvantage to you, if you're owed money back," said Jackie Perlman, principal tax research analyst at The Tax Institute at H&R Block.

Of course, people have plenty of reasons for not filing tax returns.

"Some taxpayers know that their refunds will be applied against debt such as past-due child support or other obligations so they don’t file," said Marshall Hunt, certified public accountant and director of tax policy for the Accounting Aid Society's tax assistance program in metro Detroit. "Why not file and pay down the debt?"

Your refund checks will be held by the IRS, however, if you have not filed tax returns for 2014 and 2015.

A  refund also would be applied to amounts still owed to the IRS or state tax agency. It can also be used to offset past-due federal debts, such as student loans.

Some people don't file because they don't think it's necessary.

"Some taxpayers believe that once you reach a certain age or retire, you don’t have to file anymore," Hunt said. "That might be true in some cases, but there might be refunds available from withholding or state credits."

For 2013, one did not need to file a federal income tax return if single and making less than $10,000. That threshold is $10,350 for 2016 returns. If married and filing a joint return, a federal income tax return is not required to be filed if one's income was $20,000 in 2013 or $20,700 in 2016.

Yet many times, an employer withholds federal income taxes from paychecks based on how you filled out your W-4 for withholding taxes. If you don't file a federal return, you cannot get back the money that was withheld.

Filing a tax return for 2013, of course, requires getting all the proper paperwork in place.

"Hopefully, you've saved some of these papers somewhere," Perlman said.

If not, tax filers who are missing W-2 forms would need to request copies from their employers. If you're missing 1098 forms for how much you paid in mortgage interest or how much you paid in student loan interest, you'd need to reach out to your lender or loan servicer.

If you're missing a 1099 form that can report interest you received during the year or wages for work as a freelancer or independent contractor, you'd need to reach out to the appropriate parties for those forms, too. Or you might need to find 1099 forms reporting interest income from a bank account or 1099s reporting gambling winnings.

The IRS says taxpayers who are unable to get missing forms from their employer or other payer can go to www.irs.gov and use the "Get Transcript Online" tool to obtain a Wage and Income Transcript.

The IRS notes that by failing to file a tax return, some struggling families aren't just giving up tax refund cash that was withheld or paid during 2013. Many low-income and families of modest means may have been eligible for the Earned Income Tax Credit, as well. For 2013, the credit was worth as much as $6,044.

For 2013, the income thresholds had various ranges depending on whether you had children who qualified under the credit or not.

For a single filer without a child who qualified, the income cutoff for the Earned Income Tax Credit was $14,340 in 2013. For a married couple filing a joint return, the income threshold was $51,567 if they had three or more children who qualified under the Earned Income Tax Credit rules. Other income limits applied for those with one child or two children.

Tax season can be crazy enough without having to worry about tax returns that could have been filed years ago. But why let a $1 billion just sit there?

Contact Susan Tompor: stompor@freepress.com or 313-222-8876. Follow her on Twitter @Tompor.