To edit Form 1099-B in TurboTax, return to the original entry and click Edit next to the transaction.
After a few screens, you will see Review your sales. Click the pencil icon next to the sale to edit.
Scroll down to the bottom of the next screen. There is an opportunity here to make changes to the cost basis, but select Continue.
The next screen is: Let us know if any of these situations apply to this sale, and include the option: I paid sales expenses that aren't included in the sale proceeds reported on the form.
When this box is checked, a box appears that you can enter the amount for: Sales expenses not reported on Form 1099-B.
For general information, see; Where do I enter a 1099-B?
