See http://www.finaid.org/questions/divorce.phtml for the order
[quote]
1.The parent with whom the child lived the most during the past 12 months (the 12 months ending on the FAFSA application date).
2.The parent who provided more financial support to the child during the past 12 months.
3.The parent who provided the most financial support to the child during the most recent calendar year for which either parent provided more support to the child.
4.The parent who provided more than half the child’s support (and will continue to do so).
5.The parent who has legal custody.
6.The parent who claimed the child as a dependent on their tax return.
7.The parent with the greater income