Is a 21yo son who's living @home, in college, earning under $5K/yr, w/ food, & medical & dental care paid for by his parents, is he a dependent?

[george-korchowsky]

Also, almost all expenses, including car maintenance and repair, are provided by his parents.

[Mike9241]

maybe. 

to be claimed as a dependent, he must be a full-time student. (full-time means he attended school – (online courses and correspondence schools don’t count) during any part of five calendar months during 2025(

 Your info indicates that he satisfies the other criteria for being able to be claimed as a dependent

[NCperson]

as long as he meets the full time student critieria  and lived with you for at least 6 months of the year, he is your dependent.  How much income he earned is not a criteria. 

https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent

[Hal_Al]

Q.  Is a 21yo son who's living at home, in college, earning under $5K/yr, w/ food, & medical & dental care paid for by his parents, is he a dependent?

A. Yes. If his income is less than $5200, he can be a dependent, even if he is not a full time student.  

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, full time student status, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income credit. They are interrelated but the rules are different for each.

The support test is different for each type. The support test, for a QC, is only that the child didn't provide more than half his own support. The support test for a Qualifying Relative is that the taxpayer provided more than half the relative's support.

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 excluded from the support calculation
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 himself.

The support value of the home, provided by the parent, is the fair market rental value of the home plus utilities & other expenses divided by the number of occupants.

The IRS has a worksheet that can be used to help with the support calculation. See: http://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf

A person can still be a Qualifying relative dependent, if not a Qualifying Child, if he meets the 6 tests for claiming a dependent:

1. Closely Related OR live with the taxpayer ALL year
2. His/her gross taxable income for the year must be less than $5200 (2025) ($5050 for 2024).
3. The taxpayer must have provided more than 1/2 his support

In either case:

4. He must be a US citizen or resident of the US, Canada or Mexico
5. He must not file a joint return with his spouse or be claiming a dependent of his own
6. He must not be the qualifying child of another taxpayer

See full dependent rules at: https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Ret...