These are not TurboTax errors. Form 1040X does not report Form 1040 Line 16a because it is nontaxable. Furthermore, if you were going to file a federal amended tax return, you would not need to include an updated Form 1040 even if it was completed (see Assembling Your Return below).
If you would like to file an amended federal tax return, you could do so since Form 1040X Part III provides a space to explain changes.
Per the Instructions for Form 1040X (https://www.irs.gov/pub/irs-pdf/i1040x.pdf:(
Assembling Your Return
Assemble any schedules and forms behind Form 1040X in order
of the “Attachment Sequence No.” shown in the upper-right
corner of the schedule or form. If you have supporting
statements, arrange them in the same order as the schedules or
forms they support and attach them last. Don’t attach a copy of
your original return, correspondence, or other items unless
required to do so.
Attach to the front of Form 1040X:
- A copy of any Form W-2, Form W-2c, or Form 2439, Notice to
Shareholder of Undistributed Long-Term Capital Gains, that
support changes made on this return;
- A copy of any Form W-2G, Certain Gambling Winnings, or
1099-R that support changes made on this return, but only if tax
was withheld; and
- A copy of any Form 1042-S, Foreign Person's U.S. Source
Income Subject to Withholding; Form SSA-1042S, Social
Security Benefit Statement (Nonresident Aliens); Form
RRB-1042S, Payments by the Railroad Retirement Board
(Nonresident Aliens); or Form 8288-A, Statement of Withholding
on Dispositions by Foreign Persons of U.S. Real Property
Interests, that support changes made on this return.
Attach to the back of Form 1040X any Form 8805, Foreign
Partner's Information Statement of Section 1446 Withholding
Tax, that supports changes made on this return.
If you owe tax and you don’t want to pay electronically,
enclose (don’t attach) your check or money order in the
envelope with your amended return. See the instructions for
line 20, earlier.
