You can, most likely, still claim him.
A child of a taxpayer can still be a “Qualifying Child” (QC) dependent, regardless of his/her income, if:
1. He is under age 19, or under 24
if a full time student for at least 5 months of the year, or is totally &
permanently disabled
2. He did not provide more than 1/2 his own support
3. He lived with the parent
(including temporary absences such as military training*) for more than half
the year
So, it doesn't matter how much he earned. What matters is how much he spent
on support. Money he put into savings does not count as support he spent on him
self.
The support value of the home you provided is the fair market rental value
of the home plus utilities & other expenses divided by the number of
occupants.
Furthermore, there is a rule that says IF somebody else CAN claim him as a
dependent, he is not allowed to claim his own exemption. If he has sufficient
income (usually more than $6300), he can & should still file taxes; he just
doesn’t get his own $4000 exemption (deduction). In TurboTax, he indicates that
somebody else can claim him as a dependent, at the personal information
section.
Even if he had less, he is allowed to file if
he needs to get back income tax withholding. He cannot get back social security
or Medicare tax withholding.
*Even though he moved out before the middle of the year; the time in basic training and even advanced individual training, is still considered as living with you. Until he gets his permanent duty station; his residence is where he lived prior to enlistment.