Where in tax return to write off a bad investment in a company start-up whose stock has no value as company out of business?? How to enter details for loss carryforward?

Yes, you may report this as an investment loss.

Enter this under the Investment Income area of Personal Income.

1. Choose Personal >> Personal Income, then I’ll Choose What I Work On.
2. Investment Income >> Stocks, Mutual Funds >> Start/Update.
3. Type of Investment: Everything Else
4. Enter a description, Net Proceeds = $0, and date of sale = date of dissolution.
5. Acquired: Whatever method
6. Cost Basis: your investment
7. Date of Acquisition: date you made your investment

TurboTax will calculate the loss on this investment and determine if it was short- or long-term. If you have other capital gains, the loss will offset some or all of the gains. Otherwise, up to $3,000 of the capital loss will go to line 13 of Form 1040 and offset other income. The remaining loss over $3,000 will be carried forward each year until used up (applied to capital gains and/or ordinary income).