@fbgoldwing wrote:
In 2016 I had a substantial net operating loss when I filed my taxes using TurboTax Home & Business, but it did not carry that loss over to 2017 or 2018.
The problem you are faced with at this point is for a 2016 net operating loss (NOL), you either must carry the NOL back two years before you can carry it forward (for twenty years) or you had to attach a statement to your original return filed by the due date (including extensions) for the NOL year (2016) to waive the carryback period.
Since you apparently did not attach a statement waiving the carryback period for 2016, you can only amend previous returns (such as 2014 and 2015) to include the 2016 NOL and then carry the NOL forward (assuming it has not been absorbed) on returns thereafter.
See https://www.irs.gov/pub/irs-prior/p536--2016.pdf
Note that for NOLs arising in tax years after 2017, the only option is to carry the NOL forward.
