did you have a lot of adjustments in the 1099 (wash sales, AMD, non-covered securities) etc that prevented you from entering those at detailed level onto Form 8949 (and the rest can be input as sales summaries without adjustment). That's what is usually triggering the need to mail the 1099 in the first place (or upload which is only available for online), but it's probably avoidable in a lot of cases.
