Please visit the link below to view the response from PatriciaV regarding Form 8453.
No one answered the question as to how one can upload Form 8453 to the Turbo Tax return. I think perhaps the answer is that it is not possible. That is unfortunate. TurboTax should make it possible to add Form 8453 and to upload PDFs of Form 1098-C. Can anyone comment on this?
Form 8453 is literally titled "U.S. Individual Income Tax Transmittal for an IRS e-file Return" and is used to submit forms that the IRS requires you to mail in even if you e-file. The IRS will never release coding for this form and other attachments that should be mailed in for TurboTax to add to the software. This is why the link provided by ChondelLO points to the answer that states that Form 8453 must be mailed.
If you need that form and TurboTax did not add it, you can get a copy in the FORMS section of www.irs.gov