I have this same question. I have always aggregated in the past few years (for those stocks where basis is being tracked by broker of course) and used various sales date and various purchase date to report multiple stock sales together.

This year Proseries has changed and doesn't allow various for sales date. AND at the link below it says "The IRS does not allow Various as a date sold, even if reported a summary of the stock."

Is this true? I can't find guidance from the IRS to that point.