After a lengthy conversation with the friendly Turbotax rep, I discovered that there is no way to include an attachment that is not requested by the IRS--if you're filing electronically. If you're sending your return by mail, you may include attachments. I think you really need to weigh the pros and cons--you apparently take a risk when mailing returns to the IRS (greater possibility of errors, potential security issues, etc). I opted to file electronically--if the IRS requests clarification, I'll take care of that at a later date. [The risk here is, of course, that may delay your refund. The IRS requested clarification last year on my son's return, and it took him 10 months to get his refund.}
By the way, if you have the business edition of TT, there is a way to upload an attachment, but this feature is apparently limited to a specific form.
