NEW YORK (CNNMoney) -- If you still haven't filed your 2008 tax return, you could be missing out on some serious cash.
The IRS said Thursday it has $1 billion in unclaimed tax refunds waiting for the one million people who still haven't filed a federal income tax return for 2008. Half of these refunds are worth more than $600, the agency estimates.
And time is running out to collect. In order to get a refund for tax year 2008, you need to get your return to Uncle Sam no later than April 17. After that, any money left over becomes the property of the U.S. Treasury.
The IRS said that some people may not have filed returns because their income was low enough that they weren't required to file. But if they had taxes withheld from their wages or made quarterly estimated payments, they could still be owed a refund.
Plus, failing to file a return means you could miss out on certain tax credits. For example, if you didn't receive an economic stimulus payment in 2008, you may have been eligible for the Recovery Rebate Credit of up to $600 per taxpayer.
You could also miss out on the chance to claim the Earned Income Tax Credit, a refundable credit for low- to moderate-income working Americans.
The amount of the unclaimed tax refunds vary by state. Wyoming residents are missing out on the fattest payouts, with a median potential refund of $773, while Oregon residents are owed the smallest amounts -- a median of $527.
Even if you are owed a refund, the IRS has a few conditions before it will release the money. For instance, you may not be able to collect an unclaimed refund for 2008 if you haven't filed tax returns for 2009 and 2010.
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