I don't think my situation was exactly what @JamesG1 described. My 1099-B entries did not add up within a certain line. For example, one entry in the short-term section may look like this (numbers are made up):
Short-term Proceeds: 70
Short-term Cost Basis: 100
Short-term Gain or loss: -20
The "expected" loss would be -30, but it was written as -20. This is because $10 of this was converted from short-term to long-term capital loss.
Separately, I found there was an entry in the long-term section that would correspond to this conversion:
Long-term Proceeds: 0
Long-term Cost Basis: 0
Long-term Gain or Loss: -10
This entry them made the overall loss sum to the correct amount, and I guess it handled converting the appropriate portion of it to long-term.
Turbo Tax allowed me to enter the proceeds and cost basis for each line, but didn't allow me to adjust the gain/loss. It's possible that selecting I need to correct the holding period would have helped, but I didn't explicitly try that - and I don't know if it would've allowed me to correct the holding period only for a portion of the entry.
@LeelaBell I ended up fixing this by just manually adjusting the cost basis of each entry so that the final gain/loss number was correct. As far as I'm aware (although I'd be happy for anyone to correct me if I'm wrong), the final sums for gain/loss in each section are what ends up mattering rather than the specific cost basis for each entry.
