If all of you are living together as a family then only one parent should claim the child; the other parent should not enter anything about the child on their tax return. If you used your child's SSN on your tax return, you have put that number into the system and your GF cannot e-file using the child's SSN now. The only way she can file and claim the child is to file by mail. When your return has been fully processed, you will need to amend to remove the child from your return.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
