Thank you for replying! After your answer I looked into my broker giving a correct form, and found this page from my broker which states that box 2a is often inaccurate, and that the account holder has to file form 8606: https://www.betterment.com/resources/common-tax-form-questions/#16
The IRS page you sent has instructions for filling out from 4852.
I'm not sure which I need, but does that link I just included change your opinion on this? Do you know how I can have Turbotax create the form I need?
Thanks again
