Forget about the huge Powerball jackpot, there's a much bigger amount still waiting to be claimed -- $2 billion worth of tax refunds.

The IRS owes the money to more than 1.5 million people who never filed tax returns for 2002. Half could get checks worth more than $500.

"We want people to get the refunds they're entitled to," IRS Commissioner Mark Everson said Tuesday. "Taxpayers can't get a refund if they don't file a return."

The bad news is it will be gone forever, if you don't act fast.

To collect the refunds, taxpayers must file a 2002 tax return before this year's April 17 filing deadline. The IRS urges taxpayers to check their records and seize the opportunity to claim their money.

"They have until April 17 this year to claim a refund," said Christopher Miller of the IRS.

People due a refund, in many cases, did not make enough money to be required to file a tax return but paid too much in taxes during the year. Taxes could have been withheld from paychecks, or a self-employed taxpayer may have made tax payments on earnings.

Gavin Langer didn't make enough as a part-time groundskeeper in 2002 to have to file a federal return, but he still may have a refund coming.

"$500? I could use that big time right now," Langer said.

If the money goes unclaimed it goes back into the U.S. Treasury.

There's only one way to get it.

"You can't get the refund if you don't file a return," Miller said.

There is no penalty for filing late if you're owed a refund, but if you don't file it by April 17, the federal government keeps the cash.

Current and prior year tax forms and instructions are available on the IRS Web site or by calling (800) TAX-FORM.

Taxpayers who need help also can call the IRS help line at (800) 829-1040.