The broker didn't report the cost basis to the IRS because they don't have to. They only have to do this for "covered securities" [1], which include stocks you

The broker didn't report the cost basis to the IRS because they don't have to. They only have to do this for "covered securities" [1], which include stocks you buy with cash, but don't include stocks you acquire as employee compensation. [1] https://www.irs.gov/instructions/i1099b#idm139900428766768 https://www.irs.gov/instructions/i1099b#idm139900428766768