Most divorce decrees order the parties to exchange income information at regular intervals so that the parties can evaluate whether child support should be changed due to changes in the circumstances. If the parties are agreeable then they can petition the Oklahoma Department of Human Services (if the support is collected and distributed through them) or a private lawyer to change the child support computation and order to reflect the updated information.
This, of course, is a very optimistic view regarding how child support is changed. Very often child support is a bitterly disputed aspect of the child custody arrangement even if the parties have agreed to it. The payor often thinks they are being robbed and that the receiving parent is wasting the money while the paying parent often depends on that money for the household to function.
The law, in turn, is very clear about child support. The parents of children are obligated to support their children and because the parents very often have divergent views about what that should be the legislature has taken the calculation largely out of their hands by establishing the Oklahoma Child Support Guidelines which nearly all courts will uniformly enforce in the absence of a bona fide agreement between the parents and occasionally even despite that if the arrangement appears to the court to be unfair to one parent or the other.
When the parties handle changes to child support through counsel, a Motion to Modify Child Support is filed with the District Court for the review of the assigned judge. If the Motion is contested then the judge will set a hearing date and order that evidence be exchanged and usually order the parties to appear at a pretrial hearing to determine if there are genuine issues of fact for the determination of the Court. If there are such issues then a trial on child support will be held and the court will determine the facts and circumstances of the parties and order child support accordingly.
A Motion to Modify Child Support will often be combined with other motions such as modifications to visitation and modifications to custody as both of these things can drastically affect the amount of child support that a party might owe.