Thank you for your kind response.
(One of ) My broker(s) is reporting the transaction as a "covered". So they are reporting both the cost basis and the proceeds.
Would it not be simpler to just show the loss through that 1099-B rather than through a form 8949 "Box C" checked transaction? (Which has not been reported to the IRS)
Forgive me for "second-guessing" you here, I just want to do what's right to minimize my risk of having to deal with an audit.
(To further complicate things, these ETF shares were purchased through two brokers - one reported it as a covered transaction with both basis and proceeds, the other was "unknown term", "basis not reported to IRS".)
Thanks again for your very helpful insight.