I got rid of and wrote off in 2016 these stocks and on my 1099 it shows up as an incomplete transaction.
Incomplete transaction? Not sure what that means. Do you mean that the transaction went off as a worthless security? If you received any proceeds from the sale of these they have to give you that information on the sell side. If you received nothing it is a worthless security transaction. If you purchased these securities prior to 2011, your broker is correct - they do not have to report the cost basis. If you purchased these securities prior to 2011 they are considered "non-covered" and the broker only has to provide you with the proceeds amount (they also only report to the irs proceeds and no cost basis for pre 2011). You can still fill out the sch D and put your cost basis in yourself. As long as you have backup - like old confirmations of the purchase you can use the cost basis against the sale whether you got proceeds that were less or if they were worthless.