Also keep in mind that, when filing MFS in general, you both must itemize or both claim the Standard deduction. And there are additional issues if you are in a Community Property State. Furthermore, you can't claim the EITC if your filing status is MFS.
Congress over the years has enacted these rules so that married couples do not "game the system" by filing MFS to get higher refunds. In addition, the Head of Household filing status is designed for Single parents with children.
