MAGI is calculated differently for different purposes throughout the IRS, so it does depend on why you are asking. What line items is there income between lines 1 and 11 on Form 1040?
also, were you going to claim him? if he is NOT a student, he made more than $4300 so he can't be claimed
You have not mentioned your son's age or whether he was a student in 2021. In order to help you determine if you can claim him as a dependent we need to know those things. And .....why are you looking for his MAGI? What are you trying to do?
He is 17 in HS. I use State assisted insurance and they want me to put this info in.
As NCperson said, there are different definitions of MAGI for different purposes. There isn't one way to calculate MAGI for all purposes. If it's the state insurance that's asking, you have to look in the instructions that they give you, or ask them exactly how to calculate MAGI for the state assisted insurance.