What forms are required for a mailed in filing?

[JohnB5677]

All forms will be included if you printed your return for filling with TurboTax. 

Attach Forms W-2 and 2439 to Form 1040 or 1040-SR. If you received a Form W-2c (a corrected Form W-2), attach your original Forms W-2 and any Forms W-2c. Attach Forms W-2G and 1099-R to Form 1040 or 1040-SR if tax was withheld.  

See assemble your return under Requirements for a Paper Return

[Kronick97]

The answer to my question may be more complex than it seems since my first option was to e-file my tax return.

The e-file option requires a security affirmation of prior year adjusted gross income.  Turbotax does not have access to my prior 3 years of adjusted gross income as those annual returns were all filed by mail although the preparation was completed within TurboTax software. 

[Cass0317]

If you used the CD/Download version, you need to view your saved returns for the last 3 years that have the file ending in .tax20XX (correct year) or the pdf file saved on your computer or backup. Search your computer for all files ending in .tax. Check in One Drive, Drop Box etc. it should be in your Documents then in the Turbo Tax folder. You can also try this, start the program, then go up to File-Open and see if it finds your file.

If you are unable to locate your files, see the alternative ways to locate your AGI on the IRS website here: Validating Your Electronically Filed Tax Return

To find your AGI, please see the following TurboTax FAQ's:

How do I find last year’s AGI?

Why can't I find my return in Tax Home or My Docs™?

The amount can be located on:

Form 1040 - Line 38

Form 1040A - Line 21

Form 1040EZ - Line 4

[Kronick97]

I filed my 2021 Form 1040 tax return by mail because TurboTax E-Filing requires confirmation of the prior year Adjusted Gross Income.  Since I have been unable to E-File a form 1040 for the past 4 years, TurboTax does not have any electronic record of prior year Adjusted Gross Income values.  Consequently, asking for prior year Adjusted Gross Income is a non-starter for attempting current year E-Filing of Form 1040.  IRS agents have confirmed that TurboTax does not have access to any Federal taxpayer records for confirmation of any taxpayer adjusted gross income values.