If you are divorced and your child would like to apply for college financial aid, the Free Application for Federal Student Aid (FAFSA) should be completed by the residential or custodial parent, meaning the one with whom the child has resided the most within the last 12 months. If the divorce is reatively recent or if the time spent with each parent is about equal, then the FAFSA will be completed by the parent who has provided the most financial support. Finally, if the decision is till close, the financial aid director will be the one who makes the ultimate decision.
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