If I had 'custody' of the child until 10/17 can I claim her on my 2017 taxes? Should I mail my return with a copy of the custody papers since someone else claimed her?

[DanielV01 · Accepted solution]

You probably can claim her and yes, you should mail in your proof.  Since you had her for 10 months, the only way you could lose the claim is if her father can prove that she was with him for a longer time.  No other relative, assuming you are the mother, can claim her no matter how long they stayed with her.  Here's a TurboTax website that gives more information:  What Happens When Both Parents Claim a Child on a Tax Return ...