You actually end up showing this very similar to having purchased stock in a company and then it became worthless. The following is where you would go to report this in TurboTax.
You enter your stock sale (startup loss) information by
clicking on
Federal Taxes
then on
Wages & Income
then on
I'll choose what I work on
scroll down to
Investment Income
on the
Stocks, Bonds, Mutual Funds, Other line, click Start or update
follow the interview to enter your security sale info.
Your purchase date will be the date you invested the money in the start up.
Your sales date is the date it became worthless (probably date it closed down)
Sales Price would be $0 (unless you got something)