Can I add a supplemental schedule to me e-file?

I have additional details regarding a capital loss which I believe would preempt IRS questions and would like to include a 1 page pdf to my e-file.

posted

Nothing like that can be attached to an e-file return. Your only option to submit it with your return is to mail your return and then hope that such an irregular form is not just thrown in the trash when it gets to the clerk that will enter your return's data. However, your letter should not be necessary if you got a 1099-B and the cost basis reported was correct.