How do I correct cost basis that was not reported in a 1099-B?

1. Open your return (if it's not already open) and search inside TurboTax for the phrase stock sales.
2. Click or tap the "Jump to" link in the search results.
3. Answer Yes to both Did you sell any investments? and Did you get a 1099-B?
   • If you land on Here's the investment sales info we have so far, select Add More Sales. Then answer Yes to Did you get a 1099-B?
4. When asked how you want to enter your 1099-B, select I'll type it in myself.
5. Select or enter your brokerage on the next screen and continue.
6. On the following screen (Tell us about...) select the second option, I'll enter a summary.
7. On the same screen, enter the total proceeds (sales) and cost basis, along with the sales category. Refer to your 1099-B for the amounts and category. When finished, select Done.
8. Follow the onscreen instructions to enter additional sales or to view a summary.

When you are done entering all your sales transactions, you'll eventually come to the Here's the investment sales info we have so far screen. Here you can edit, delete, or enter more sales.