@nexchap The part of the interview that let's me enter the "correct" cost basis is not appearing if I check said box. However, after some experimentation, I believe I discovered why. This is how I fixed it:
1. Created an entirely new 1099-B entry in Turbotax via "Add investments".
2. Entered the sale information for the items I needed to adjust cost basis (for me, it was three separate line items in my 1099-B; I entered them as three separate items).
3. Checked "The cost basis is incorrect or missing on my 1099-B" for each transaction.
4. Next screen: None of these apply.
5. "We noticed there's an issue with your cost basis..." appears for these transactions.
6. Entered the correct cost basis.
After this, I went back to the original 1099-B that lists the transactions that needed the cost basis corrected, and deleted them, so the transactions aren't listed twice in my return.
I believe this is a bug associated with the autoimport functionality. I used the autoimport to import my investment data (can't remember if I did it via uploading the PDF file, or direct download from my instituation; I believe it was the latter).
