After you file

There is no such thing as 50-50 for the IRS.  The children spent more nights with one of you than with the other.  If you have an agreement to trade off in alternate years, then honor your agreement.  You cannot both claim the same child in the same tax year unless one of you signs 8332 that gives the custodial parent EIC and childcare credit, and awards child tax credit and the personal credit to the other parent.
**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.**