If you sold stock in 2007 and 2008 but did not take a loss on your income tax return, no, you can not go back and file amended income tax returns, to reflect the loss. Generally, it's no longer possible to claim a tax year 2012 or earlier refund, as the 3-year statute of limitations has expired.
You also cannot claim a 2007 and 2008 stock loss on your 2016 income tax return.
