You misunderstood the rules and tried to put the child on two tax returns. Only divorced or never married couples who live APART can say there is a signed agreement and "share" the child-related credits. If you all live together as a family you can only enter the child ---and all of the child related credits--on ONE of your tax returns. The other parent files as Single and does not enter anything at all about the child on their return.
You can amend and use ALL of the credits---your partner files as Single with no mention of the child on their return. Then work out sharing privately between the two of you.
**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.**
