How do I mail in my 8949 with my 1099-B statements?
You don't. If you e-file your 1041 then you need to e-file your completed 8949 along with it. Otherwise, you need to print and mail the entire return.
See https://www.irs.gov/instructions/i1041sd#en_US_2023_publink100035978
If Form 1041 is e-filed, then any Schedule D (Form 1041) and Form 8949 that are part of the return must also be e-filed.
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