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.
<a rel="nofollow" target="_blank" href="
https://www.thebalance.com/claiming-same-dependent-audit-risk-3193030">https://www.thebalance.com/cl...>
