Child support can be modified as often as it needs to be, provided there’s been a substantial change in circumstances. The decision of whether a substantial change in circumstances has taken place is judged based upon a comparison of what child support is now and what it would be under the new income circumstances or parenting time circumstances. If the new formula changes the amounts by more than 20 percent or at least $75.00, there’s a presumption that you’ve met the standard for change.