With this year's tax deadline less than a month away, the Internal Revenue Service is warning that there still are millions of dollars awaiting Iowa and Illinois taxpayers who did not file a federal tax return for 2010 — but time is running out.

The IRS estimates that refunds totaling $7.1 million may be waiting for 9,200 Iowans who did not file and $32.7 million may be waiting for 37,900 taxpayers in Illinois. The refunds could mean at least $576 for the Iowa taxpayers and at least $626 for the Illinois taxpayers.

But in order to collect, taxpayers must file their 2010 tax return by April 15, 2014.

As IRS Commissioner John Koskinen points out "The window is quickly closing ... We encourage students, part-time workers and others who haven't filed for 2010 to look into this before time runs out on April 15."

The IRS said that the law generally allows a three-year window for claiming a refund and if no return is filed in that time-frame the money becomes property of the U.S. Treasury. The law requires that the return by properly addressed, mailed and postmarked by April 15 this year. There is no penalty for filing a late return that qualifies for a refund.

"In some cases, people may not have filed because they had too little income to require filing a tax return," said Christopher Miller, the IRS spokesman for Wisconsin, Iowa and Nebraska. "But by not filing it, they're leaving behind money withheld from their check and potentially leaving behind refundable credits like the Earned Income Tax Credit."

Get breaking news sent instantly to your inbox

Miller added that nationally about 20 percent of the taxpayers who are eligible for the EITC do not claim it. The credit, available to many low- and moderate-income workers, was worth up to nearly $5,666 for 2010.

Taxpayers seeking a 2010 refund also are reminded to have filed for subsequent years as well. In fact, unclaimed refund checks for tax year 2010 may be held if taxpayers have not filed returns for 2011 and 2012. Refunds also will be applied to any amounts still owed to the IRS, unpaid child support or past due federal debts, such as student loans. 

Current and prior year tax forms and instructions are available at IRS.gov on the Forms and Publications page or by calling toll-free 800-TAX-FORM (800-829-3676).

Taxpayers missing Forms W-2, 1098, 1099 or 5498 for the 2010, 2011 or 2012 years should request copies from their employer, bank or other payer. If unsuccessful, taxpayers can get a free transcript showing information from these year-end documents by going to IRS.gov.