I would just agree on an amount with the NCP and give back the extra every month without going through the courts. You never know what will come up when you start getting the courts involved. Or if the NCP is providing the medical insurance mail the extra in on the premiums so he isnt covering all of the support. Put the extra in a savings account for graduation, first car, college, etc. That would still help both parents. I am sure he will not be opposed to either one. Be carefull with going to court in my state they only like to modify child support every three years. If you petition to lower it and something happens that you need the extra support (unexpected illness,injury,loss of job,etc.) then you have to go back to the courts and NCP may not be so agreeable to increase support then you have the expense of modification. Anything you can agree on outside of court is in your best interest.