It is your option to summarize for e-File however,
IRS requires details to be listed on Form 8949,
or on your own forms (e.g. consolidated 1099-B) which have the same information and in the same manner as Form 8949.
Either way, if you choose to summarize, you have to mail those transaction details to the IRS within three business days of IRS accepting your tax return.
Exception: transactions in category A or D without adjustments do not require form 8949. No mailing is necessary.
