In most states the parents of a minor child may agree to the amount of child support, and courts encourage the parents to do so. But the court will generally review the agreed amount of child support and determine whether it is in the best interest of the child before signing a child support order. And if the parents later agree to change the amount of or need for child support, they should return to court and get a signed order that reflects the agreed or changed amount, as only the court may change the legal obligation under a child support order.

In Montana, as in most states, parents of a minor child can negotiate and agree upon the amount of child support. The state encourages such agreements as they can be more amicable and tailored to the specific needs of the family. However, any agreement on child support must be reviewed and approved by a court to ensure that it meets the child's best interests. Montana courts use child support guidelines to determine the appropriate amount of support, which considers factors such as the income of both parents, the needs of the child, and parenting time. If parents wish to modify an existing child support order, they must petition the court for a modification. The court will then review the request and decide whether the change in circumstances justifies a modification of the support amount. It is important to note that any informal agreement between parents that is not court-approved does not change the legal child support obligations.