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.
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.
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.
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
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.
Net income only. Gross income minus all mandatory deductions gives net income which is used for the combined income calculation and economic table lookup.
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.
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.
Use our 2026 Washington State estimator to see how these legal terms impact your support amount. All calculators are RCW 26.19 compliant.