Understanding the Income Shares Model

The Income Shares model is the most widely used method for calculating child support in the United States, used by 41 states. This guide explains how it works.

The Basic Concept

The Income Shares model is based on a simple principle: children should receive the same proportion of parental income they would have received if the parents lived together.

Rather than looking at just one parent's income, this model considers what both parents earn to determine the total support needed.

How It Works

Step 1: Calculate Combined Income

Both parents' gross monthly incomes are added together:

Parent A: $5,000/month
Parent B: $3,000/month
Combined: $8,000/month

Step 2: Determine Basic Support Obligation

Each state has a table showing how much parents typically spend on children at different income levels. For example, with $8,000 combined income and 2 children, the table might show $1,400 as the basic support obligation.

Step 3: Calculate Each Parent's Share

Each parent's share is proportional to their income:

Parent A: $5,000 / $8,000 = 62.5%
Parent B: $3,000 / $8,000 = 37.5%

Step 4: Add Additional Expenses

Extraordinary expenses are typically added:

• Health insurance premiums for children
• Childcare/daycare costs
• Uninsured medical expenses

Step 5: Calculate Final Amount

The non-custodial parent typically pays their percentage of the total:

Basic obligation: $1,400
Health insurance: $200
Childcare: $400
Total: $2,000

If Parent A is non-custodial:
$2,000 × 62.5% = $1,250/month

States Using Income Shares

41 states use this model, including:

• California, New York, Florida, Texas
• Pennsylvania, Ohio, Illinois, Georgia
• And many more

Check our state reference for your state's model.

Adjustments and Deviations

Courts may adjust the calculated amount based on:

• Shared custody: If both parents have significant time (often 30%+ overnights)
• Multiple families: Supporting children from other relationships
• High income: Amounts may be capped or adjusted
• Special needs: Children with extraordinary expenses
• Travel costs: Long-distance visitation expenses

Pros and Cons

Advantages

✅ Considers both parents' ability to pay ✅ Based on actual child-rearing costs ✅ More equitable than percentage-only models ✅ Accounts for shared custody fairly

Disadvantages

❌ More complex to calculate ❌ Requires accurate income information from both parents ❌ Tables may not reflect actual costs in high-cost areas

Calculate Your Estimate

Use our Child Support Calculator to get an estimate based on the income shares model. Enter both parents' incomes, number of children, and custody arrangement for a personalized calculation.