The IRS reported that roughly one million taxpayers did not file their 2011 federal income tax returns, resulting in $1 billion in unclaimed refunds. IRS Commissioner John Koskinen stated that student and part-time workers were likely among those who could receive larger refund checks.
It's projected that the majority of the refunds are for $600 or more, but taxpayers will have to submit their 2011 returns by April 15, 2015 to be eligible. The IRS also notes that 2011 refunds could be withheld if 2012 or 2013 returns have not been filed.
Source: Internal Revenue Service