you can't just forward a 1099-B to the IRS.
you will have to amend your tax return (Form 1040-X) to show on Form 8949 the cost basis col(e) for your proceeds col(d) so that it is not all taxable
I would be replying in writing to the letter to tell the IRS you will be filing an amendment within the next three business days.
when filing 1040-X on paper,
Do not include your old 1040 nor your revised 1040 because the Form 1040-X reflects any changes there and becomes your new tax return.
@AaronHxZ
