What kind of 1099 do you have? There are over 20 different kinds. There is no plain Form 1099. All 1099 forms have one or more letters after the 1099. The most common are 1099-INT, 1099-DIV, 1099-B, 1099-NEC, 1099-R, and 1099-G.
If you are talking about a 1099-B, the form reports a sale on which you have a loss. You enter the sale under Investment Income > Stocks, Cryptocurrency, Mutual Funds, Bonds, Other." You enter the details of the sale, including the proceeds and basis. TurboTax will calculate the loss and include it in your tax return.
