The 3 year limit is for refunds, not for amending tax returns (although the IRS sometimes dislikes processing them past 3 years).
Also, the Statute of Limitations for NOLs is 3 years back from the NOL year. So as long as the NOL year is within 3 years, you can amend (and get refunds) for 3 years before THAT. See Section 6511(d)(2).
<a rel="nofollow" target="_blank" href="
https://www.law.cornell.edu/uscode/text/26/6511#d">https://www.law.cornell.edu/uscode/text/26/6511#d...>
