The IRS has over $1 billion in unclaimed refunds for one million people who did not file their 2008 tax return. The agency estimates that over half of these refunds are $637 or more.

Some of these people didn’t file their 2008 return because they had too little income, even though they had taxes withheld or made quarterly estimated payments.

If you were part of the group who didn’t file in 2008, then there are a couple things to keep in mind regarding your potential refund collection.

First, the law provides most taxpayers with a three year window of opportunity for claiming a refund if they did not file. The 2008 window will close on April 17, 2012.

And second, the IRS may hold the refund check if the taxpayer did not file returns for 2009 and 2010. Also, the refund may be applied towards any amount to the agency, or it may be used to offset unpaid child support or past due federal debts such as student loans.

So, there is still time left to file your 2008 tax return if you haven’t already done so. And with the IRS holding a billion dollars worth of refunds for a million taxpayers, you might even get a check from the agency in the mail.