The new tax law eliminated the deduction for personal theft losses (which includes fraud) for 2018. You'd have to do an amended return for the year in which the loss occurred. You can't use an online version of TurboTax to do a previous year's return. If you wanted to use TurboTax you'd have to purchase the previous year's CD/Download version.
https://turbotax.intuit.com/personal-taxes/past-years-products/
I have the previous years turbotax loaded on my computer. I need to file my 2018 return by Oct 15, should I file the 2018 return or go back and amend previous returns before I file the 2018 return?
The deadline for filing an amended return to claim a refund is 3 years from the date the original return was filed, or 2 years from the date the tax was paid, whichever is later.
I used the 2016 Turbo Tax to file an amended return for that year for 550,000.00 theft loss and I will be getting about a 32,000.00 refund. Can I report a loss on an amended return for 2017 for part of that same loss?
See "When to Report Gains and Losses" on pages 15-16 of IRS Publication 547: https://www.irs.gov/pub/irs-pdf/p547.pdf
That pub is for 2018. I am asking about how do I determine a carryover theft loss from the 2016 amended return to an amended return for 2017.
IRS Publication 547 for tax year 2016 - https://www.irs.gov/pub/irs-prior/p547--2016.pdf