April 17, 2007 will be the last chance to claim a refund for a 2003 return that was not extended. Likewise, if you need to amend your 2003 return to claim a refund, the deadline will be April 17 if you did not extend the return. The statute allows you to claim a refund if you file the return within 3 years of the due date, including extensions. After that, you will no longer receive the refund.
This is true even if you owe taxes for another year subsequent to 2003. Unfortunately, many people wait too long to file those overdue returns and end up paying unnecessarily. So, if you are expecting a refund for 2003 and you have not filed 2004 and expect to owe, get that return in as soon as possible.
If you do end up filing a return for a refund for 2003 at the last minute, make sure you mail the return Certified Mail, Return Receipt Requested. If you do not, they will find a reason to show the return was not filed on a timely basis.
