He is living and working in Illinois, so Illinois is his tax home.
Having a New York driver's license is not enough to establish a tax home in New York.
As a dependent student, he would be a resident of the same state as the state in which the person that claims him lives,
HOWEVER
from your description, it sounds like he is now a non-dependent and filing on his own.
It also sounds like he is a resident of Illinois and would file as such.
Since he is a non-dependent for all of 2024 (you did not supply more than half his 2024 support and the child did not live with you after graduating) he will file as a full-year Illinois resident and not file for New York. (unless he has income from NY sources, in which case he would file as a non-resident for New York).
Having a New York driver's license is not enough to establish a tax home in New York. He is living and working in Illinois, so Illinois is his tax home.
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