Do I need a custody agreement? As both a family law attorney and a single mother I cannot more strongly recommend that separating parents adopt a formal custody agreement. My ex and I have a custody agreement. We have had it since we separated 7 years ago. We have never needed it. We agree on every schedule, we speak freely and compromise easily for each other's sake. But, it is there, if anything ever changed it is there and it is the foundation of the great co-parentin