"Can I report that as a loss in my investments in TT, and if so, how? Do I report it as a sale of $0?"
Essentially that's correct.
Using the "Stocks, Bonds, Mutual Funds, Other" interview, tell TurboTax that you have a sale NOT reported on a 1099-B. Assuming you know the correct basis to use - which almost certainly isn't simply what you paid for it - simply tell TurboTax that what you sold was "stock". Enter the basic information about the sale, with a proceeds of $0 and a date sold of 12/31/18. You can tell TurboTax you bought the stock, (you really did using a combination of cash and "sweat equity"), with a purchase date the same as the exercise date, then enter the basis information. On the "Special Situations" page tick "worthless".
Tom Young
