Child Support Calculations in Washington

Washington uses the Income Shares model to calculate child support, governed by RCW 26.19. The schedule estimates what an intact household would spend on children at various income levels and allocates that amount between parents. Whether you're navigating an uncontested or contested divorce, understanding how Washington calculates child support is essential.

The Income Shares Model

Washington's Income Shares model determines the basic support obligation from the Washington State Child Support Economic Table based on combined monthly net income and the number of children. The schedule provides per-child amounts that already account for family size.

Current law (through December 31, 2025): The economic table is presumptive for combined monthly net income up to $12,000. Above this cap, courts may exceed the presumptive amount with written findings.

Effective January 1, 2026: Major changes extend the presumptive table to $50,000 combined monthly net income, with a floor raised to $2,200 CMNI.

Determining Net Income

"Net income" is gross income minus allowable deductions. Gross income includes nearly all sources:

• Salaries, wages, commissions, bonuses, and overtime
• Self-employment income (net of ordinary and necessary expenses)
• Dividends, interest, trust income, and capital gains
• Pensions, retirement, workers' compensation, and unemployment
• Maintenance (spousal support) received

Allowable deductions include: Federal/state income taxes, FICA, mandatory pension contributions, mandatory union dues, state industrial insurance premiums, and court-ordered maintenance actually paid.

Excluded: New spouse/partner income, child support received from other relationships, TANF, SSI, and food stamps.

Parenting Time Adjustments

Unlike many states with fixed overnight thresholds, Washington uses a discretionary deviation approach for parenting time:

• No automatic credit: Even a 50/50 schedule does not automatically reduce support
• Evidence required: The court may deviate if the child spends "significant time" with the obligor and evidence shows increased costs to that parent and decreased costs to the recipient
• Protection for recipient: Courts will not deviate if it would leave insufficient funds in the recipient household to meet the child's basic needs or if the child receives TANF

Split custody: When each parent is the primary residential parent for at least one child, Washington uses a residential split adjustment method with offsetting obligations.

Estimate Your Washington Child Support

Use our calculator to get a preliminary estimate. For official calculations, use the Washington DCS Child Support Calculator.

Self-Support Reserve and Caps

Washington protects low-income obligors through several mechanisms:

• Self-Support Reserve (SSR): Currently 125% of the federal poverty guideline ($1,569/month as of January 2024); increases to 180% FPG effective January 1, 2026
• $50 minimum: Per child per month, unless unjust under RCW 26.19.065(2)
• 45% cap: Neither parent's total basic child support for all biological/legal children may exceed 45% of net income, absent good cause

Health Insurance, Childcare, and Add-Ons

Beyond the basic obligation, Washington requires allocation of additional expenses:

• Health care: Insurance premiums and ordinary uninsured medical costs are not in the table and must be shared pro rata by income
• Work-related childcare: Daycare costs are added and shared proportionally
• Special child-rearing expenses: Tuition, long-distance travel for parenting time, and other educational/special needs costs may be ordered and shared pro rata

Common Calculation Mistakes

• Expecting automatic overnight credit: Washington does not use a fixed threshold—parenting time deviations require evidence and court findings
• Using outdated caps: The $12,000 CMNI cap changes to $50,000 on January 1, 2026; the SSR increases from 125% to 180% FPG
• Forgetting the 45% cap: Total support for all children cannot exceed 45% of net income without good cause
• Missing imputation rules: Courts may impute income if a parent is voluntarily unemployed or underemployed
• Ignoring add-ons: Health insurance, daycare, and special expenses are separate from the basic obligation

Modification and Duration

Washington provides multiple pathways to modify support:

• Substantial change: Any party may seek modification at any time upon substantial change of circumstances
• 24-month adjustment: After 24 months, support may be adjusted based on income changes or schedule/table updates without showing "substantial change"
• DCS threshold: The Division of Child Support may file if the order is at least 15% above or below the standard calculation
• Phased implementation: If a change exceeds 30% and causes significant hardship, courts may implement it in two equal steps six months apart

Duration: Support ends upon emancipation (age 18) or death of the obligor. Courts may extend support for high school completion. Postsecondary support is discretionary, typically not extending beyond age 23.

Enforcement and Interest

Washington provides robust enforcement tools:

• 12% interest: Unpaid child support judgments accrue interest at 12% per year
• Income withholding: Standard for most orders; payments go to the Washington State Support Registry (WSSR)
• License suspension: Driver's, hunting/fishing, professional, and business licenses may be suspended for nonpayment
• Tax refund intercepts: State and federal refunds can be seized
• Liens and levies: Property, bank accounts, and vehicles may be subject to liens or seizure

Key Takeaways

• Income Shares model: Basic obligation from economic table, allocated by income shares
• $12,000 cap (2025): Rises to $50,000 effective January 1, 2026
• No automatic overnight credit: Parenting time deviations are discretionary with evidence requirements
• SSR protection: 125% FPG ($1,569/month) through 2025; 180% FPG starting 2026
• 45% cap: Maximum total support for all children
• 12% interest: Accrues on unpaid child support judgments

For more information about Washington divorce processes, see our Washington divorce timeline and filing checklist.