How do I enter my adjusted cost basis for my grantor trust?
For the sales listed on your 1099-B, you may need to enter their adjusted cost basis. To add this information in TurboTax:
Open or continue your return.
Navigate to the 1099-B section:
TurboTax Online/Mobile: Go to 1099-B.
TurboTax Desktop: Search for 1099-B, and select the Jump to link.
On the Did you have investment income in 2025? screen, select Yes.
If you’ve already added some investment info, select Add investments.
On the Let's import your tax info screen, search for your bank and import your forms.
If you don’t want to import your info, select Enter a different way, then Stocks, Bonds, Mutual Funds.
Continue until you get to the Now, choose how to enter your sales screen, and select One by one then Continue.
On the Review your sales screen, select the pencil icon next to one of your sales.
You may not see this screen if you chose to enter your 1099-B another way.
On the Now, enter one sale on your 1099-B screen, check the box next to The cost basis is incorrect or missing on my 1099-B and select Continue.
On the Let us know if any of these situations apply to this sale screen, check the box next to None of these apply and select Continue.
On the Do you need to adjust your cost basis screen, select Yes, I need to adjust my cost basis and enter the amount.
You can find your adjusted cost basis on a supplemental form provided by your financial institution. It’s usually available by mid-February along with Form 1099-B.
Select Continue.
Your adjusted cost basis has been added for your sale. Repeat steps 5-9 for any other sales you need to modify.
