When it comes to child support (and often also spousal support) it is inevitable that at some point after you receive an order from the judge that the income of one of the parties will change. When this happens you are under a fiduciary duty to notify the other side of your income change (and them to tell you about their income changes). After notification either party can move for a modification. The amount will then go up or down based on the financial situation (and custody time if child support) that the parties currently have.
You do this by filing a Request for a Modification Order. Along with this will come filing a revised Income and Expense declaration and providing the other party with copies of your paystubs, and also possibly taxes. The court will then put these equations into the magic calculator (also known as dissomaster) and come out with the new support payment amounts.