In Missouri, generally, for a parent to modify child support, they must show a substantial and continuing change in circumstances that warrant a change in support.  Missouri law states that if there is a 20% increase or decrease in the incomes of one of the parents, that, by itself, will meet the change in circumstances requirement.  However, according to a recent ruling by the Missouri Court of Appeals, that will only apply if the Form 14 presumed amount of child support is used. 

In Selby v. Selby, the Missouri Court of Appeals for the southern district held that when a child support amount is based on an agreement between the parties deviating from the Form 14, in this case an agreement to zero, then a party wishing to modify will have to show that they cannot support the child/ren in a manner contemplated at the time of the agreement.  Although it may be the case that the income of a parent has changed by more than 20%, that by itself will not be enough if the moving party can still support the children in the same manner as before.  It would appear that evidence of the children’s current expenses, evidence as to how much the children’s expenses have increased, and evidence of the change in parties income in the intervening years would need to be shown.