My wife and I have claimed our 3 year old granddaugther on our taxes. She lives with us along with her mother . The babys father wants to claim her. Can he do that?

[fac95]

He does not live with us and they are not married.

[Bsch4477]

He can’t claim her based on tax law. Of course there is nothing to prevent him from trying. But if he tries it after you claimed her, his return will be rejected. If he claims her before you do, you would have to file by mail. The IRS would then send both of you letters to justify your positions. You would win. 

[Opus 17]

Legally speaking, he can’t claim her as a “qualifying child“ dependent because she does not live in his home more than half the year.  He can’t claim her as a “qualifying relative“ dependent, because, regardless of the other tests for that type of dependent, a child can’t be claimed as a qualifying relative dependent by one taxpayer if they can already be claimed as a qualifying child dependent by another taxpayer.  Both you and the child’s mother seem to live with the child more than half the year, which means that either you, or the mother can claim the child as a qualifying child dependent. That means that the father can’t claim the child, even if you were willing to allow it. (He can’t claim the child because the child can be claimed by you, so even if the child is not actually claimed by you, he is still disqualified.)

[Hal_Al]

Q. My wife and I have claimed our 3 year old granddaughter on our taxes. She lives with us along with her mother . The baby's father wants to claim her. Can he do that?

A. Yes, but only with the written permission of the baby's mother, on IRS form 8332.  Otherwise, no. 

Bottom line: the mother (the custodial parent*) gets to decide who can claim the child. Of course, the person she selects must meet the rules. When a child lives with the mother and the grandparents, she can almost always allow the grandparents to claim the child (no written form or written permission is required).  See rules below, particularly #6 (your income must be higher than the mother's income)

If she wants the father to claim the child, instead of the grandparents, she can do that by sending him form 8332.  Without form 8332, he cannot legally claim the child. 

A child closely related (grandchild counts) to a taxpayer can be a “Qualifying Child (QC)” dependent, regardless of the child's 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
3. He lived with the relative (including temporary absences) for more than half the year
4. He is younger than the relative (not applicable for a disabled child)
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 (this essentially means that you have the parent’s permission to claim the child, if the child also lived with the parent more than half the year)
6. If the parents of a child can claim the child as a qualifying child but no parent so claims the child, no one else can claim the child as a qualifying child unless that person's adjusted gross income (AGI) is higher than the highest AGI of any of the child's parents who can claim the child.

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

*The IRS goes by physical custody, not legal custody. So, for tax purposes, there is no such thing as "joint custody".

[Opus 17]

One other thing to point out is that the father can put anything on his tax return that he wants, but it doesn't make it right.  If he tries to claim the child as a dependent and someone else also claims the child, the IRS will send letters to start an investigation.  Each person who claimed the child will be asked to prove they meet the conditions of claiming a dependent--such as that the child lives with them, etc.  You can't stop the father from trying to claim the child (and starting an investigation), but as already described, the father does not have legal standing to claim the child unless the mother voluntarily allows it, which must be done in writing.   Even then, certain special rules apply.