"Our son who we allowed to claim himself as a dependent"
You're not allowed to do that. If he qualifies as your dependent*, he cannot claim himself, even if you don't actually claim him.
What is it you're trying to accomplish? 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. However, he usually only qualifies for an education credit or deduction, if he is not a dependent (see exception below).
If he is trying to claim an education credit, you should be aware that there are restrictions on a student claiming himself and getting the refundable portion of the American Opportunity credit. A student, under age 24, is only eligible if he supports himself by working, even if he is not a dependent. He cannot be supporting himself on student loans & grants, parental support and 529 plans. If the student actually has a tax liability, there is a provision to allow him to claim a non-refundable tuition credit. But then the parent must forgo claiming the student as a dependent, and the $500 other dependent credit. The student must still indicate that he can be claimed as a dependent, on his return. If the student is using some of the educational expenses to claim a credit or deduction, the parent cannot claim the same expenses against the 1099-Q (double dipping).
*A child of a taxpayer can still be a “Qualifying Child” (QC) dependent, regardless of his/her income, if:
- 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
- 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.
- He lived with the parent (including temporary absences such as away at school) for more than half the year
