Income Shares Model vs Percentage of Income: Child Support Formulas Compared
The Income Shares model pools both parents' incomes to simulate total intact-family child expenditures and divides costs proportionately, adjusting directly for overnight custody. The Percentage of Income model looks exclusively at the paying parent's income, applying a flat percentage (e.g. 20% for 1 child) regardless of what the custodial parent earns or how parenting time is shared.
Feature Matrix: Income Shares Model vs Percentage of Income Model
| Feature | Income Shares Model | Percentage of Income Model |
|---|---|---|
| State Adoption | 41+ US States (including IL, IN, FL, CA, NY, OH) | ~6 US States (including TX, WI, NV, MS, ND) |
| Considers Custodial Income? | Yes (Pooled combined income) | No (Strictly ignores custodial income) |
| Overnight Timesharing Adjustment | Graduated credits for overnight visitation | Rarely adjusts without formal judicial deviation |
| Healthcare & Daycare Add-Ons | Divided proportionally based on income shares | Added on top of flat percentage |
Income Shares Model
An economic child support framework pooling both parents' incomes and dividing the child's financial needs proportionately.
Key Advantages
- Considers both parents' earnings fairly, avoiding disproportionate burdens.
- Smoothly integrates overnight parenting time credits for shared custody.
- Reflects real-world marginal costs of child-rearing at various income tiers.
Limitations
- More complex mathematical formulas requiring financial disclosure from both sides.
- Can lead to frequent recalculation disputes if parental incomes fluctuate.
Percentage of Income Model
A traditional child support model establishing support strictly as a flat percentage of the non-custodial parent's income.
Key Advantages
- Simple, predictable, and transparent math with fewer disputes.
- Custodial parent's income does not need to be verified or disclosed.
Limitations
- Ignores high-earning custodial parents whose children need less transfer support.
- Often punishes paying parents who exercise significant overnight custody.
1. Why Most States Shifted to the Income Shares Framework
Frequently Asked Questions
Which child support model yields higher payments?
It depends on the custodial parent's income. When the custodial parent has low or zero earnings, the Income Shares model often produces higher support. When the custodial parent earns more than the paying parent, the Income Shares model results in substantially lower payments.