Either parent can ask the court to modify child support and either to increase or decrease the amount.
In order to ask for a change in respect of those children who are under 19 and unmarried, you will have to prove that one parent is either earning more or less than before which will result in a change of the amount of child support by more than 10% upwards or downwards, or that something else has happened to change the financial situation of either or both parents.
In order to start the process, firstly you need go to the clerk of the court who is based in the same county where your current child support orders came from. There you ask for two forms, the Request to Change Child Support form and the Child Support Obligation Income Statement form, complete them and hand them back in. The other parent will be advised of your filing of the documentation and will also be advised of the date of the hearing.
Your request for amendment will be heard in front of a judge and he has up to 45 days to give his ruling but often he will decide straight away. At the hearing you should bring evidence to support your request such as pay slips, tax returns, bank statements or any social security statements. You are also allowed to bring witnesses if they know about the changes in circumstance and they can provide back up to your claim.