My son turns 18 this year. What are the exact guidelines (including his income level) that determine whether I could count him as a non-child dependent or not for 2018?

[dawnzetta]

Under the 2017 laws, a dependent cannot make over $4050.  I cannot find if this applies to 2018 or not.  The only vague wording I can find is that the credit is for non-child dependents who live with you.

[Hal_Al · Accepted solution]

18 is still a child. 19 is the  age threshold (24 if a full time student).

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, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income Credit.

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 considered third party support and not as support provided by the student.

3. He lived with the parent (including temporary absences such as away at school) for more than half the year

 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 $4,050 (2016-17), $4150 (2018)

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

[dawnzetta]

Can you tell me where you found the info about the $4150 threshold for qualifying relative dependents?  That is  exactly what I have been looking for.

[Hal_Al]

The qualifying relative rules have not changed for 2018. So, you won't find anything specific to 2018. You will find where the personal exemption has been inflation adjusted to $4150 for 2018.
But that is somewhat academic as the dependent and personal exemptions go  away starting in 2018. So, there will be no longer be a deduction for having a non child dependent. There will be a new $500 "non-child dependent" non-refundable tax credit available (and that's scheduled to go away in 5 years)