I'm confused because I've found language online that says he needs to be under 19, but the help box here on Turbo Tax said 19 and under. That is an important distiction for me.
You are correct that a dependent child must be under 17 years old.
However, he may be eligible as Qualifying Relatives.
"A qualifying relative must meet general rules for dependents and pass these tests:
Please see the IRS publication Dependents for more details.
Provided they meet these guidelines, you can claim them as dependents.
In order to claim your 19 year old as a dependent ---- if he was NOT a student in 2024 he can be claimed if he had less than $5050 of income in 2024. If he is NOT a student and had at least $5050 of income, he cannot be claimed as anyone's dependent. If he was a student in 2024, income over $5050 does not prevent you from claiming him.
WHO CAN I CLAIM AS A DEPENDENT?
You can claim a child, relative, friend, or fiancé (etc.) as a dependent on your 2024 tax return as long as they meet the following requirements:
Qualifying child
Qualifying relative
When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them. There may be other tax benefits you can get when you claim a dependent.
Related Information: