You will need to mail in your return.
If you were the first to
e-file, their return will reject. If someone else claimed your child when they
shouldn't have, and if they file first, your return will be rejected. The only
way to claim your child is to file a return on paper. The IRS will process your
return and send you your refund.
Usually within a few
months, you'll receive a letter from the IRS, stating that your child
was claimed on another return. If you made a mistake, 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,
removing the child from their
return, the IRS, will require you to
provide proof. There will be a list of possible ways you can do this. The more
you can provide, the better your chances.
The non-custodial parent
can only claim the child as a dependent if the custodial parent gives
permission (on form 8332) or if it's on the divorce decree.
Below are links to the type of proof the IRS may request.
https://elite8financial.com/wp-content/uploads/2017/01/f886-h-eic.pdf
https://www.eitc.irs.gov/eitc/files/downloads/f886-h-hoh.pdf
https://www.eitc.irs.gov/eitc/files/downloads/f886-h-dep.pdf
