OK, just a guess at this point since you didn't say "What For" yet, and since you are filing a 1040SR
...IF...if wanting to know MAGI for IRMAA purposes? (Medicare part B and Part D premium payments).
MAGI for that purpose is Line 11 plus line 2a of your form 1040 or 1040SR.
__________
Thing is, if you have not actually filed your 2022 taxes yet (you're really late), I'm not sure whether SS/Medicare will use your 2022 MAGI or your 2021 MAGI to calculate your IRMAA premiums for 2024, since they normally would use your 2022 MAGI.
....but they don't know that 2022 value yet, and they are setting up their payments for 2024 right now..
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
