For Amended 2020 return, TT printed form 8453 (boxForm 8949). I mailed this info with 2020 filing, should I mail it again with the amended return?

[JohnW152]

You only need to send in Form 8453 if you’re attaching one or more of the forms or supporting documents listed on the form, and only if your amended return was electronically filed.

[fanfare]

To answer your question, with Form 1040-X, you do not mail a second time the information you mailed under cover of 8453.

In any case, that info goes to a separate IRS office.

A big problem with TurboTax is that it does not print the forms to be attached to form 1040-X (see instructions).

It gives you your entire revised return and you have to figure that out yourself by inspection.

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.