If you do not believe the calculation is correct you can appeal but first, you must ask for mandatory reconsideration which is where the CMS reconsider the calculation. If you still wish to challenge it, you can apply to the Social Security and Child Support Tribunal within one month. You can apply out of time but you will need to give your reasons for doing so. The family team at Osbornes are expert in child maintenance cases. We can advise you on the best course of action for your family and help you to reach a fair and legally binding agreement. To learn more, please get in touch and we will be happy to help with anything you need.