Indiana Income Shares Child Support Formula Explained

May 29, 2026

The Income Shares Model

Indiana’s child support system is based on the Income Shares model — the premise that children should receive the same proportion of parental income they would have received had the parents remained together. Both parents contribute to the child’s support in proportion to their income.

This contrasts with the older “percentage of income” model (used in states like Illinois) where only the NCP’s income determines the obligation.

Step-by-Step Calculation

Step 1: Gross Weekly Income

All income sources count: wages, salary, bonuses, overtime, self-employment net, rental, dividends, Social Security (disability/retirement), unemployment, workers’ comp. Weekly income is the base unit; convert monthly ÷ 4.333 or annual ÷ 52.

Step 2: Adjusted Weekly Gross Income (AWGI)

AWGI = Gross Weekly Income
       − Court-ordered prior child support paid
       − Court-ordered spousal maintenance paid

Only court-ordered, legally binding payments qualify as deductions.

Step 3: Combined Weekly Adjusted Income (CWAI)

CWAI = NCP's AWGI + CP's AWGI

Minimum meaningful income for the schedule is $100/week combined. Below this, the court determines an appropriate amount case by case.

Step 4: Basic Support Obligation (BSO)

Look up the BSO from the Indiana Guideline Schedule using CWAI and number of children. The schedule was updated January 1, 2024 using the Rothbarth expenditure model with 2013-2019 Consumer Expenditure Survey data.

Step 5: Add-On Expenses

Total Support Obligation (TSO) = BSO
  + Weekly work-related childcare costs
  + Weekly children's health insurance premium

These are added before the proportional split. Each parent pays their proportional share of the add-ons.

Step 6: Income Proportion and NCP’s Raw Obligation

NCP income proportion = NCP's AWGI / CWAI
NCP raw obligation    = TSO × NCP income proportion

Step 7: Parenting Time Credit

Applied when the NCP has 52+ overnight visits per year. The credit is a percentage of the NCP’s share of the BSO only (not the add-ons):

PTC = BSO × NCP proportion × credit percentage

Credit percentages increase with overnight count per the 2024 graduated table.

At 183+ overnights (near-equal parenting), the BSO is multiplied by 1.5 to reflect two-household costs, and the higher-earning parent pays the net difference between the two parents’ obligations.

Step 8: Final NCP Obligation

Final obligation = NCP raw obligation − Parenting Time Credit

Minimum: $0 (cannot be negative). The obligation cannot exceed 50% of the NCP’s AWGI in most circumstances.

2024 Guideline Changes

Schedule update: BSO amounts increased 4-22% across income brackets using updated economic data reflecting current child-rearing costs.

Uninsured medical expenses: The automatic 6% add-on for uninsured medical expenses was eliminated. All uninsured medical costs (above $100 per child per year in prior law) are now split proportionally from the first dollar, using the same income proportion used for the TSO.

Low-income floor: The floor was raised from $290/week gross (based on one minimum-wage job) to $580/week (two minimum-wage jobs), providing a higher baseline income floor for the NCP in low-income cases.

Parenting time averaging: When different children in the same order have different overnight schedules (e.g., one child lives primarily with NCP, another with CP), a new averaging method determines the blended parenting time credit.

Use the Indiana child support calculator to apply the full Income Shares formula with your specific income figures, parenting time, and add-on expenses.