It depends on the exact meaning of "a full time student for about 3 months". For dependent purposes, the student rule is "a student for any part of 5 calendar months. The 5 months do not have to be consecutive. The common example: a kid who was a student from January 30 to May 1 ("about" 3 months) meets the 5 month rule.
There are two types of dependents, "Qualifying Children"(QC) and Other ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit, student status, a relationship test and residence test.
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 excluded from the support calculation
- He lived with the parent (including temporary absences such as away at school) for more than half the year
If your kid does not qualify under the QC rules, then he must have less than $5050 of income to qualify under the Qualifying Relative rules.
See full dependent rules at: https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Ret...
