The amount of child support is determined according to the Washington State Child Support Schedule. The Court then Orders each parent to pay the amount of child support using the standard calculation. This is true even if the parents informally agree between themselves to a lower transfer payment. However, special circumstances in a given situation may warrant the Courts adopting a different amount of child support for the obligated parent to pay. This is called a support deviation.

Reasons for a support deviation from the standard calculation of child support include income of other adults in the household; possession of wealth; extraordinary debt not voluntarily incurred; a significant disparity in living costs of the parents due to conditions beyond their control; and special medical, educational, or psychological needs of the children. Also considered is whether the parents have other children to support and where the children spend a significant amount of time with the parent who is obligated to make the child support transfer payment. The mere agreement of the parents is not a sufficient reason for a deviation of child support.

The Court may not deviate if the support deviation will result in insufficient funds in the household receiving the child support to meet the basic needs of the child or if the child is receiving aid to families with dependent children.