Child support is mandated by law and is calculated based upon a percentage of income. If both parties are employees earning income that is reported on a W-2 form at year’s end, the calculation is a simple mathematical computation. The percentages are 17% for one child, 25% for two children, 29% for three children and 31% for four children. The percentage is computed on a party’s gross income, less Social Security, Medicare and New York City income tax. The percentages apply to the first $143,000.00 of income. Beyond that amount, the court has discretion to apply the percentages or some lesser amount. While these calculations seem simple, they become very difficult when one party is self-employed or in a cash-based business. In such a situation, the court will try to determine a party’s true income in order to apply the percentages. The court is not bound by a tax return, and may impute income to a party in appropriate circumstances.