Ex wife has "sole legal and primary physical custody of the minor children" in our decree. Son has since turned 18 and lives with me FT. Can I claim him as a dependent?

[SweetieJean]

When did he move in with you?

[BobinCT]

Did he turn 18 in 2017?

[Hal_Al · Accepted solution]

Yes, if he lived with you for more than half of 2017.

If your ex files a competing return, claiming the child, the IRS will rule in your favor. They go by actual physical custody not legal custody. 

[IreneS]

You may be able to claim your son as a dependent if he meets the five tests for a qualifying child and a dependent--relationship, age, residency, support, and joint return.

1.  Relationship - He's your son -- no problem there.

2.  Age - A child must be:

• Under age 19 at the end of the year; 
• A student under age 24 at the end of the year; or
• Permanently and totally disabled at any time during the year, regardless of age.

3.  Residency - Your child must have lived with you for more than half the year. [Being away at college is still considered living with you (for tax purposes).]

4.  Support - The child can't have provided more than half of his or her own support for the year.

5.  Joint return - To meet this test, the child can't file a joint return for the year.