@dmertz, thx for the response.
Following is the TT's explanation for how it got the number, I am not sure "TurboTax performs the calculation as described in the information that you got from the IRS.".
Generally, the amount on line 12 (MAGI of the IRA worksheet) will be the amount shown on line 9 (total income) of Form 1040 not including the IRA deduction on Schedule 1 (Form 1040), line 19, the student loan interest deduction on Schedule 1 (Form 1040), line 20, the tuition and fees deduction on Schedule 1 (Form 1040), line 21, series EE bond interest exclusion from Form 8815, excluded adoption benefits from Form 8839, nor the foreign earned income and housing exclusion from Form 2555, line 45. It will include the adjustments on Schedule 1 (Form 1040), lines 10 through 18a, and any amount entered on line 22.
1040/1040SR Wks Adjusted Gross Income xxxx.
Plus the following adjustments added back to Adjusted Gross Income
Schedule 1 IRA deduction xxx
Schedule 1 Student loan interest deduction
Schedule 1 Tuition
Form 8815 Line 14
Form 8839 (Untitled) Line 28
Form 2555 p3-T Line 45
Form 2555 p3-S Line 45
In addition to the above adjustments, if unemployment is excluded on this return under the American Recovery Plan Act of 2021, the amount of unemployment excluded will be added back as well. This amount can be found on line 8 of Schedule 1 with the description "UCE". For example, if Schedule 1 line 8 contains a line with the description "UCE" and an amount of -$10,200, then $10,200 (as a positive amount) will also be added back to Adjusted Gross Income.
However, if you or your spouse also received a distribution from a traditional IRA, a special calculation is made to determine the amount on this line and may not agree with the amount on line 8b of Form 1040.
