No, you cannot also claim somebody that has been claimed on his own return. One person = one exemption.
But it's not optional which return he gets claimed on. So, the real question is should he have claimed himself , on his return. 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.
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. Scholarships are considered third party support and not as support provided by the student.
3. He lived with the parent (including temporary absences such as away at school) 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.
If he/she has filed a return, claiming himself, he will need to file an amended return, unclaiming himself, so that you can claim him. You do not need to wait until his amended return is fully processed, to claim him on your return. But, you cannot e-file. You will have to mail in a paper return.
UPDATED 8/22/19. Despite the May 31, 2019 date, above, this is a 2018 or earlier question and answer.
With the tax law change, effective 2018, most students will get the same refund whether they claim themselves or not. The personal exemption has been eliminated and the standard deduction increased. This assumes that most of their income is earned income (wages or self employment) and/or taxable scholarship. Dependents use a special calculation for the standard deduction (their earned income [including scholarships] + $350).
