How Child Support Works
Child support is determined by state guidelines and is designed to ensure children maintain a comparable standard of living in both households. About 40 states use the income shares model, which combines both parents' incomes to determine what would have been spent on children in an intact household. Each parent then pays their proportional share based on income.
Under the percentage-of-income model, used by states like Texas and Wisconsin, support is calculated as a flat percentage of the noncustodial parent's income: typically 17% for one child, 25% for two, 29% for three, and 31% for four or more. Courts consider additional factors including healthcare costs, childcare expenses, special needs, and the custody arrangement.
Child support is modifiable when there's a substantial change in circumstances — a significant income change, a change in custody arrangement, or a change in the child's needs. Most states allow modification requests when income changes by 15-20% or more.
Add-On Expenses
Beyond base child support, courts typically require parents to share certain additional expenses proportionally. These commonly include childcare costs necessary for the custodial parent to work, health insurance premiums for the children, uninsured medical and dental expenses, educational expenses including tutoring and school supplies, and extracurricular activities agreed upon by both parents. These add-ons are usually split in proportion to each parent's income share.