Business & farm

Do you mean a non-business bad debt?  You may claim the nonbusiness bad debt deduction as explained in this TurboTax Help.

In addition, IRS Publication 550, page 84, explains nonbusiness bad debts.

To enter the form manually In TurboTax Premium Online, follow these steps:

1. Down the left side of the screen, click Federal.
2. Down the left side of the screen, click Wages & Income.
3. Click the down arrow to the right of Investments and Savings.
4. Click to the right of Stocks, Cryptocurrency, Mutual Funds, Bonds, Other (1099-B).
5. Click Add investments.
6. On the Save time and connect your financial accounts screen, select Type it in myself.
7. On the OK, let's start with one investment type screen, select Other, then Continue.
8. At the screen Tell us more about this sale, enter the information.  Click Continue.
9. On the screen Now, enter one sale for nonbusiness bad debt, enter the information.
10. What type of investment, select Other.
11. How did you receive it, select Something else.
12. Enter the the term 'worthless' within the Description.
13. Report it as a short-term sale.
14. Enter $0 for Proceeds.
15. Enter the amount of the loss for Cost or other basis.
16. Select Continue.