How Child Support Works in the United States
Child support in the United States is governed entirely by state law, with no federal divorce statute. However, the federal Child Support Enforcement (CSE) program under Title IV-D of the Social Security Act (42 U.S.C. § 651-669b) provides the framework for interstate enforcement and requires states to establish uniform guidelines reviewed every four years per 45 C.F.R. § 302.56.
The Three Child Support Calculation Models
Every state follows one of three calculation models to determine child support amounts:
Income Shares Model (40 States) The most common approach, used by states including California, Florida, New York, and Illinois, combines both parents' incomes to estimate what the family would have spent on the child if intact. Support is then prorated based on each parent's percentage of combined income. For example, if combined monthly income is $10,000 and the guideline percentage for one child is 20%, the basic support is $2,000—split proportionally between parents.
Percentage of Income Model (6 States) Alaska, Mississippi, Nevada, Wisconsin, North Dakota, and Texas base support solely on the paying parent's income. Texas uses a varying percentage: 20% for one child, 25% for two, 30% for three, 35% for four, and 40% for five or more children under Texas Family Code § 154.125. Wisconsin applies a flat 17% for one child, 25% for two, 29% for three, 31% for four, and 34% for five or more.
Melson Formula (3 States) Delaware, Hawaii, and Montana use this approach that first ensures each parent's basic needs are met before calculating support, incorporating a self-support reserve and standard of living adjustment.
State-Specific Examples
California (Family Code § 4055) California's complex algebraic formula considers each parent's net disposable income, time-share percentage, and tax filing status. Senate Bill 343, effective September 1, 2024, revised the "K factor" calculation to make support more equitable for low-income parents. The state provides a certified online calculator, though it was temporarily decertified in December 2025 following federal tax changes from H.R. 1.
Texas (Family Code § 154.125-154.129) Texas applies percentage guidelines to the non-custodial parent's net resources only. For one child, the guideline is 20% of net monthly income up to a cap of $9,200 (as of September 2023). The court may deviate based on factors like the child's special needs, travel costs for possession, or significant parenting time.
New York (Domestic Relations Law § 240) New York combines parental income up to a statutory cap ($163,000 combined annual income as of 2024), applies a percentage (17% for one child, 25% for two, 29% for three, 31% for four, 35% or more for five+), then allocates based on each parent's share of combined income. The custodial parent's share is presumed spent directly on the child.
Florida (Statute § 61.30) Florida's income shares model considers gross income, health insurance premiums, child care costs, and the number of overnights each parent has. Substantial time-sharing (at least 20% of overnights) triggers an adjusted calculation that reduces the higher-earning parent's obligation.
Modification Standards
Child support can be modified when circumstances change substantially. Federal law requires states to review orders upon request showing changed circumstances. Most states define "substantial" as either:
- A percentage change (typically 15-20%) in the calculated amount
- A specific time period (usually 3 years) since the last order
- Material changes like job loss, new children, or medical issues
Florida Statute § 61.14 requires a 15% change within three years or 10% change after three years. New York Domestic Relations Law § 236 permits modification after three years or a 15% income change. Texas Family Code § 156.401 allows modification for "material and substantial change" or every three years.
Enforcement Mechanisms
The U.S. has robust enforcement tools for collecting unpaid child support:
Wage Garnishment Under the Consumer Credit Protection Act (15 U.S.C. § 1673), employers can withhold up to 50% of disposable earnings (60% if not supporting another family), increasing to 55% or 65% if arrears exceed 12 weeks. Most states automatically issue income withholding orders with new support orders.
Federal Tax Refund Intercept The Treasury Offset Program intercepts federal tax refunds for parents owing $500+ in arrears ($150+ for public assistance cases). In fiscal year 2024, TOP recovered over $3.8 billion in delinquent child support. The IRS announced policy changes effective October 2024 affecting how 42 states access this program through contractors.
Additional Tools
- Passport denial for arrears exceeding $2,500 (42 U.S.C. § 652(k))
- Driver's license and professional license suspension
- Credit bureau reporting
- Bank account levy
- Property liens
- Criminal prosecution for willful non-payment (federal: 18 U.S.C. § 228)
When Child Support Ends
Termination ages vary significantly by state:
| State | Basic Termination Age | Extensions |
|---|---|---|
| California | 18 | 19 if still in high school |
| Texas | 18 | High school graduation or 19 |
| New York | 21 | May include college expenses |
| Florida | 18 | High school graduation |
| Mississippi | 21 | Age of majority is 21 |
| Colorado | 19 | 21 if still in high school |
Support does not terminate automatically—the paying parent must file a motion or the order must specify an end date. Courts may extend support for disabled adult children or, in some states like Indiana and New Jersey, for post-secondary education expenses.