You may still file tax returns for previous years. There is a three year limit to claim a refund. This means, you must file 2015 by tomorrow, if you want a refund. I suggest you get a mailing receipt from the post office, if you file.
Forms: <a rel="nofollow" target="_blank" href="
https://www.irs.gov/forms-pubs/prior-year">https://www.irs.gov/forms-pubs/prior-year</a>
