How much can a dependent child earn before you can't carry them as dependent?

[VolvoGirl]

How old are they?  Under 19 there is no limit.  Over 18 and not a full time student the 2020 amount is $4,300.

[Hal_Al]

Simple answer: there is no limit.

But taxes aren't simple. In actuality, there are two types of dependents, "Qualifying Children"(QC) and standard ("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:

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 him self.

But if your "child" doesn't qualify as a dependent under the QC rules, then there is an income limit of a mere $4300, for him to qualify as a qualifying relative dependent. 

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

[pjrcrush140]

My child is over 18, a full-time student and worked part time while in school.  Why does he not qualify as a dependent?

[pjrcrush140]

If my son is 25 and a fulltime student and doesn't support himself, he is still not considered a dependent?

[Hal_Al]

Q.  If my son is 25 and a fulltime student and doesn't support himself, he is still not considered a dependent?

A. Maybe

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.

Your son is too old to be a QC, so his status as full time student no longer matters. So, you then look to see if he qualifies, as a dependent, under the Qualifying Relative rules.  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 $4300 (2021).
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