Unfortunately, claiming him as a dependent on the 2011 or 2012 tax returns will not allow you to get any tax refund based on him being a dependent. The time to file a 2012 tax return for a refund has expired. You must file a tax return for a tax refund within three years from the due date of the original tax return. For tax year 2012 you needed to file the tax return on or before April 15, 2016.
