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Child support is determined by what you make. The amount and the way in which payments are made can be revisited from time to time if there has been "a change in circumstances." A change in circumstance would have occured if you were late or if you are making more or less money, if your ex spouse is making more or less money.
If circumstances have changed since the last child support order the judge can revisit that order at this time.
BTW: Payroll deduction or payment through an agency like child support enforcement is sometimes good for you as it insures a paper trail and so that you cannot be accused of paying late in the future.