I was in High School until June 2022. In July of 2022 I went active duty. Can I be dependent for half a year?

[Bsch4477]

No, you can’t split it. Whether you are a dependent depends on whether you provided more half of your support for the year. 

[DoninGA]

No, you are a dependent for the full year.  There is no half-year dependency.

Since you were a full time student in 2022 and assuming that you are under the age of 24, you can be claimed as a dependent under the Qualifying Child rules on your parent's tax return.

When you are completing your tax return you Must indicate on the return that you can be claimed as a dependent

To be a Qualifying Child -

1. The child must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, stepbrother, stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of the year, (b) under age 24 at the end of the year and a full-time student or (c) any age and permanently and totally disabled.
3. The child must have lived with you for more than half of the year. Temporary absences while away at college are considered living with you.
4. The child must not have provided more than half of his or her own support for the year.
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child must be a U.S. citizen or U.S., Canada or Mexico resident for some portion of the year.
7. The child must be younger than you unless disabled.

[Hal_Al]

As others have said, there is no half year dependents. But, what you describe indicates that you are still you parent's dependent for 2022.   That is so, for two reasons: 1. you are either under 19 or were a full time (high school)  student for 5 months and 2. you lived with your parents for more than half the year.  Being away for military training (like being away at college), including AIT, is considered only a temporary absence from the parent's home and you considered as living with them during the training time. 

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.

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 or military training) for more than half the year

So, it doesn't matter how much you earned. What matters is how much you spent on support. Money you put into savings does not count as support you spent on yourself.

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

[Carl]

In July of 2022 I went active duty. Can I be a dependent for half a year?

No. It's all or nothing. Since you went active duty in July, there's no question that you *did* provide more than half of your own support. Therefore, nobody qualifies to claim you as a dependent on their tax return.

[Hal_Al]

@Carl  Said "Since you went active duty in July, there's no question that you *did* provide more than half of your own support. Therefore, nobody qualifies to claim you as a dependent on their tax return."

I disagree.  Did he provide more than half his own support for all of 2022 is still in question. And it's the only question. It's almost certain he meets the age/student status rule and lived with the parents for more than half the year. The parents apparently provided all his support for the first 6 months and may still be providing support.  As long as he is temporarily away, for military training, the support value of the home continues.

[Carl]

If they joined in July, then they wern't enrolled in any college or trade school, and their income exceeds $4,300 for the year, with ease.

[Carl]

Also, while time spent away from home for the primary purpose of attending school, counts as time having lived at home, the same is not true for boot camp/military service. Therefore, they did not live with the parents for the entire tax year.

[Hal_Al]

Poster said "I was in High School until June 2022". That counts as student for 5+ months. H.S. is usually full time and students under 24.

I disagree, military training is considered a temporary absence from the parent's home (Pub 17, pgs 27-28).