My 1099-B shows cost basis as 0 and I don't have a supplemental form showing the adjusted cost basis. Do I need to manually calculate?

you are expected to report the true cost basis.

IRS will accept zero as your cost basis.

@bretdnixon 

Yes, you should calculate and report the correct basis.  When you enter your Form 1099-B, enter is as written but be sure to check the box for The cost basis is incorrect or missing on my 1099‑B.



Then, in a few screens, select I know my cost basis and need to make an adjustment and report the correct basis.

 

@bretdnixon