Additional information to be filed separately from eFile

[mattina]

What information from a brokerage account must be filled separately by mail?

[Mike9241]

if you do not detail type A or c where there are wash sales or any other type, you must submit an 1099-B in the same format as form 8949 using form  8453. Read its filing instructions

also, any other form specified on the 8453 can be mailed with the form rather than e-filed

https://www.irs.gov/pub/irs-pdf/f8453.pdf