The IRS regulations provide for only a "3-year look-back" meaning that one can only amend or late file to claim a refund for years that fall no more than 3 years from the deadline for filing, or from the actual date filed if earlier. This means, given we are at the end of 2016, the only tax years for which the IRS will accept amendments or late filings are 3 years back from October, 2016 : Tax Years 2015, 2014, 2013 - for late filing.
For you this means that you can still, and immediately, file an amended Form 1040x for Tax Year 2013. That said, whether you choose to accumulate all of the NOLs or only report the NOL relevant to 2013 is your choice. Do be aware that all amended filings Form 1040X are processed manually, not by computer, and this more likely to be reviewed.
So in answer to each question:
QUESTIONS:
1.) Yes, by filing Forms 1040X for 2013, 2014, and 2015 to accomplish the carryforwards.
2.) see #1
3.) No longer relevant
If this posted response is useful to you, please click on the upraised hand in the lower left of this post. Thank you. Scruffy Curmudgeon--PFFM/ IAFF, retired FireFighter/Paramedic - Locals 718/30, Veteran USAR O3 AIS/ASA '65-'67
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