Hi sorry to bring this up but I am in a similar situation. Why would you adjust the basis instead of adjusting the gain/loss? For example, if I am the primary on a joint account and have 55% ownership while the partner has a 45% ownership, wouldn't it be easier to just report 55% of the gain/loss amount? Adjusting basis sounds kind of tricky.
For example, say there's a cost basis of $100, a gain of $20 for total proceeds of $120. So updating the gain to be $11 (55% of $20) seems straightforward. Can you give an example of how you would adjust the basis to get the same result? By the way for 2022 Turbotax there doesn't seem to be an interview aspect for 1099-B. But you can edit each sale individually.
