Can I claim my grandson whom I have residential custody (court order)-mother states she's claiming him?

[Critter]

Whom did the child live with the most last year ?   Does  the mother & child live in your house with you ?

[ysmith223]

The child has been with me since April 2018 (I have residential custody) court papers. The mother moved out of state and left the child with me.

[Texas Roger]

If the child did not live with the mother more than half the year, the mother cannot claim the child as a dependent.

[BobB7]

So a key question is whether his mother lived with him for more than six months in 2018

[Hal_Al]

The  residential custody order does not give you the right to claim the child as a dependent.  IRS rules apply. The number one rule is the child must live with you more than half the year. If the child lived with both the grandparent and the parent for  more than half the year, the parent has the higher priority. In that case, the grandparent can only claim the child with the parent's permission AND if the grandparent has a higher income ( AGI) than the parent.

If the child live with you more than half the year and  lived with the parent less than half the year, then you can claim him.

[ysmith223]

I've had residential custody since April 2018. I have all receipts for clothes, footwear and aftercare and summer camp.

[ysmith223]

The mother moved out of state and left the child with me, I've been providing him.

[Critter]

Then the mother did not live with the child for more than 1/2 the year so she cannot claim the child.
And the child lived with you for more then 1/2 the year so you can claim the child ... the rules are just that simple.

[Hal_Al]

So, the mother moved away in April and left the child with you. So the child lived with you  8+ months and with the mother less than 4 months.
So, you can claim the child and the mother can't.
If the mother  claims the child inappropriately, and if she files first, your return will be rejected if e-filed. You would then need to file a return on paper, claiming the child as  appropriate. The IRS will process your return and send you your refund, in the normal time. Shortly (up to a year) thereafter, you'll receive a letter from the IRS, stating that your child was claimed on another return. It will tell you that if you made a mistake to file an amended return and if you didn't make a mistake to do nothing. The other party will get the same letter you did. If one of you doesn't file an amended return, unclaiming the child, the next letter, from the IRS, will require you to provide proof. Be sure to reply in a timely manner.
Winner gets the tax benefits; loser gets to pay the IRS back with penalties and interest.  The relative the child lives with almost always wins.  
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