What if one parent has zero income?

The working parent pays 100% of the basic obligation. However the court may impute income to the non-working parent if they are voluntarily unemployed.

Do both parents always pay support?

Each parent has an obligation but only one parent typically makes a transfer payment — the one with the higher income share who does not have primary custody.

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Core Calculation

What is the Income Shares Model in Washington Child Support?

Last updated: January 2026RCW 26.19 Compliant

Washington uses the Income Shares Model to calculate child support. Both parents net incomes are combined and used to look up the basic obligation in the economic table. Each parent then pays their proportional share based on their percentage of combined income.

Legal Definition Under Washington Law

RCW 26.19.080(1) states the basic child support obligation derived from the economic table shall be allocated between the parents based on each parent's share of the combined monthly net income.

How Income Shares Model Works in Practice

The model is built on the principle that a child should receive the same proportion of parental income they would have received if the parents lived together. Both parents contribute to the child's support in proportion to their earnings. Understanding this term is important when completing your child support calculation. Use our worksheet calculator to see how this applies to your case.

Step 1: Calculate combined net income

Step 2: Look up total basic obligation from table

Step 3: Calculate each parent's income share %

Step 4: Multiply obligation by each parent's %

Step 5: The paying parent transfers their share to the receiving parent

Real-World Example

P1 net: $6,000 / P2 net: $4,000 Combined: $10,000 P1 share: 60% / P2 share: 40% Table at $10,000 / 2 children: $1,099/child Basic obligation: $1,099 × 2 = $2,198 P1 owes: $2,198 × 60% = $1,318.80 P2 owes: $2,198 × 40% = $879.20 If P2 is the primary residential parent P1 transfers $1,318.80/mo to P2.

How Income Shares Model Affects Your Child Support Amount

Your income share percentage directly determines your obligation. The higher your income relative to combined income the larger your share. If both parents earn equal income each pays 50% of the basic obligation. This model ensures higher earning parents contribute proportionally more.

Frequently Asked Questions

Net income only. Gross income minus all mandatory deductions gives net income which is used for the combined income calculation and economic table lookup.

Need a full calculation?

Use our 2026 Washington State estimator to see how these legal terms impact your support amount. All calculators are RCW 26.19 compliant.