First question ... is this a C-corporation that started in 2018?

If not, a 2019 NOL is carried back 5 years, so it would be carried to 2014.

Second question involves your phrase "to 2018 return".  You aren't actually re-filing 2018, right?  You are just preparing the Form 1045 in the 2019 software, right?

1045 is for individuals. 1139 is for corporations.

Bill is correct you have to go back 5 years first.

1. It is not a C-Corp

2. No I am not refiling 2018, but the instructions said to go back to 2018 return and enter the NOL in screen 15

Another issue: when I do the step in 2 above, it creates a 6251 AMT amount; there was no AMT in the original return; it seems counter-intuitive to me that this should happen?

I don't see anything in the instructions that say I have to go back 5 years?

You need to enter the AMT NOL, not just the regular tax NOL.

The law changed.

https://www.irs.gov/newsroom/temporary-procedures-to-fax-certain-forms-1139-and-1045-due-to-covid-19

Where do I enter that? I entered it in Screen 15 of the 2018 return and an AMT was still created. Can I send you some PDFs?

My take on this is that you CAN go back 5 years to absorb the full NOL but you don't HAVE to. In my case, the entire NOL can be absorbed in the 2018 return.

Also, I still don't have an answer on why Lines 10 - 15 on the Form 1045 do not print. Do you you have any clue on that issue?

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@JFG wrote:

My take on this is that you CAN go back 5 years to absorb the full NOL but you don't HAVE to.

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No.  You can't pick-and-choose when to apply it.  It must be carried back 5 years.

As for your actual question, sorry, I'm a ProSeries user so I can't help you there.