As far as the IRS is concerned ---the IRS cares about physical custody and where the dependent lives. Living away at school is considered to be a "temporary absence" so you can still say he lived with you all year. If there is no signed agreement you can say NO to that question in the software when it asks.
Whether your "ex" will get contentious and try to argue about the $500 credit based on the divorce decree is a separate matter which is a legal issue.
**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.**
