New NR client has LT Capital Loss Carryover of $36K from 2016NR reported on Form 4797 (involuntary conversion). In addition, during same year, NR client had unallowed passive activity loss of $12,366.  In 2017, NR client $12,100 allowed passive loss. He’s new client to me.  His 2018 NR return shows $10K rental income (ln 18 1040NR) and after QBI ded $2K, taxable inc $8K.  Client owes $810. That's when I'm told about 2016 LT Capital Carry over loss.  Didn't see the 2016 return prior to starting my work.

Q: 2016&2017 returns done by same preparer on Proseries (competent folks).  I don’t see carryover amount on 2017.  I used the 2017 carryover wks to figure out carryover amount. I get $0. Loss was from RE investment gone bad (ponzi scheme).

Can I use that to reduce income in 2018?  Do I need to amend ‘17?

Thanks.