Business & farm

Hi, is there a deadline to file 1045?  I also have an NOL to carry back, the NOL incurred in 2016. can i still file the 1045 now to get refund for year 2014 and 2015?  I heard there's a deadline of 1 year to file thee 1045, so i dont think i can use 1045 anymore since it's over a year from tax year 2016 already?