Legal Question in Family Law in California

The subsequent actions of the parties contrary to a previous order can be a factor in modifying that order. However, it does depend on the type of order. For example, a support order must actually be modified by the court in order to change what is owed. Even if the parties agree to reduce support, the arrears can pile up.

If you are talking about a custody order, then the provable verbal agreement can be used to obtain a modification of the prior order.