Line 1 of the 2020 Form 8879 should be the same as the Adjusted Gross Income on your Federal tax return Form 1040 Line 11 for tax year 2020. Verify that the 2020 AGI is correct from your 2020 federal tax return.
If the IRS is rejecting this return for the 2020 AGI there is a possibility that the IRS does not have your 2020 AGI in their database.
Enter a 0 (zero) for the 2020 AGI and e-file the 2021 tax return again.
