The IRS estimates that half of those who could claim refunds for tax year 2004 would receive more than $552. In some cases, individuals had taxes withheld from their wages, or made payments against their taxes out of self-employed earnings, but had too little income to require filing a tax return. Some taxpayers may also be eligible for the refundable Earned Income Tax Credit.

In cases where a return was not filed, the law provides most taxpayers with a three-year window of opportunity for claiming a refund. If no return is filed to claim the refund within three years, the money becomes property of the U.S. Treasury. For 2004 returns, the window closes on April 15, 2008. The law requires that the return be properly addressed, postmarked and mailed by that date. There is no penalty assessed by the IRS for filing a late return qualifying for a refund.

The IRS reminds taxpayers seeking a 2004 refund that their checks will be held if they have not filed tax returns for 2005 or 2006. In addition, the refund will be applied to any amounts still owed to the IRS and may be used to satisfy unpaid child support or past due federal debts such as student loans.

A state-by-state breakdown of estimates for individuals who failed to file a 2004 return with a refund due is available at http://www.irs.gov/newsroom/article/0,,id=180281,00.html