Seattle Child Support Lawyers
Guiding Families through Child Support Calculation, Enforcement & Modification
Last updated March 15, 2026 // Attorney reviewed by Sara Kim, Co-Founding Partner, Blair Kim Moeller, PLLC
A child support order touches nearly every aspect of your family’s financial life — housing, childcare, healthcare, education. Yet many parents in Seattle and across King County don’t fully understand how the number on that order was reached, or what it takes to change it. Washington uses a specific statutory formula, and knowing how it works is the first step toward protecting your child’s financial future and your own. The family law attorneys at Blair Kim Moeller, PLLC help parents navigate child support — from initial calculations to contested modifications — across King, Pierce, and Snohomish Counties.
Reach out to a child support lawyer in Seattle today by calling (888) 478-4001 or contacting Blair Kim Moeller, PLLC online.
Fast Answer: Child Support in Washington
What it is: A court-ordered payment from one parent to the other to cover a child’s living, healthcare, and educational expenses, calculated under Washington’s Income Shares Model.
Governing statute: RCW 26.19 (Washington State Child Support Schedule)
Key deadline: A modification petition requires showing a substantial change in circumstances since the last order was entered — waiting too long can leave an outdated order in place.
Legal standard: The court uses both parents’ combined monthly net income and the number of children to determine the basic support obligation; the Washington child support calculator applies the schedule automatically.
Your most important next step: Gather current income documentation for both parents before any hearing — the accuracy of the calculation depends entirely on verified income figures.
Blair Kim Moeller, PLLC represents parents in child support proceedings — initial orders, modifications, and enforcement — across King, Pierce, and Snohomish Counties.
How Washington Calculates Child Support
Washington calculates child support using the Income Shares Model under RCW 26.19, which combines both parents’ monthly net incomes to determine a base obligation, then allocates each parent’s proportional share. The Washington child support calculator applies the statutory schedule to that combined income figure and the number of children. This formula produces a presumptive amount — meaning the court starts there and may deviate up or down only with specific written findings.
The first step is calculating each parent’s monthly net income. Under the Washington child support guidelines, “net income” means gross income minus certain mandatory deductions: federal and state income taxes, FICA, mandatory pension contributions, and union dues. The guidelines define gross income broadly — wages, self-employment income, rental income, unemployment benefits, Social Security, and more all count.
Once both net incomes are established, the Washington child support calculator looks up the combined amount on the statutory schedule or economic table in RCW 26.19.020. That schedule produces the “basic support obligation” — the baseline cost of raising children at that combined income level. Each parent then pays their proportional share. If Parent A earns 60% of the combined net income, Parent A contributes 60% of the basic support obligation.
The residential parent typically receives the support payment, reflecting the fact that day-to-day expenses are concentrated in that household.
Depending on the number of overnights with each parent, there may be a residential credit to the paying parent which reduces the support amount. to account for duplicated costs.
What Gets Added on Top of the Basic Obligation
The Washington child support guidelines require courts to address additional expenses beyond the basic monthly payment. These “add-on” expenses are divided proportionally between the parents based on income share and can significantly affect the total obligation.
- Health insurance premiums: The cost of insuring the children (not the parents) is added to the basic obligation and divided proportionally under RCW 26.19.080.
- Uninsured medical and dental costs: Out-of-pocket medical, dental, vision, and orthodontic expenses for the children are typically split proportionally.
- Childcare expenses: Work-related childcare costs are added to the calculation, subject to the federal childcare tax credit offset.
- Educational and functional needs expenses: Tuition for private school or special education, and costs associated with a child’s documented functional needs, may be allocated by the court.
These add-ons mean the total monthly obligation often exceeds the basic support figure. A child support lawyer in Seattle can help you document and present these costs accurately, so the final order reflects the actual expenses your children incur.
When and How Child Support Can Be Modified
Real Stories From People We’ve Helped Protect
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Frequently Asked Questions About Child Support in Washington
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Generally, a modification can be filed at any time if there has been a substantial change in circumstances. If there is no substantial change, Washington law allows a modification petition after 24 months from the last order, Filing too early without the right basis will typically result in dismissal.
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A change in the residential schedule directly affects the child support calculation. If a parenting plan is modified — for example, shifting from primary residence with one parent to an equal-time arrangement — the child support order should be reviewed and recalculated at the same time. A petition to modify a parenting plan often includes a request for modification of child support.
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Courts can impute income to a parent who appears to be concealing earnings or voluntarily reducing income to avoid a higher support obligation. Forensic financial analysis, subpoenas, and business records are tools attorneys use to expose undisclosed income. Blair Kim Moeller, PLLC’s Seattle family law attorneys have experience in high-conflict support cases where income transparency is in dispute.
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Parents can negotiate a different amount, but the agreement must be approved by a judge and incorporated into a court order to be enforceable. Informal agreements carry significant risk — they do not modify the legal obligation, and missed payments under an unmodified order create enforceable arrears.
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Under RCW 26.19.090, child support continues until the child turns 18 or graduates from high school — whichever comes later. Courts may also order post-secondary educational support if specific conditions are met, including that the child is enrolled and meeting academic standards.
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Washington child support guidelines define income broadly: wages, salaries, tips, bonuses, self-employment income, rental income, retirement benefits, Social Security, unemployment compensation, and workers’ compensation payments all count. Courts may also impute income to a parent who is voluntarily unemployed or underemployed.
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Not automatically. Even in shared-residential arrangements, Washington’s child support guidelines still require a calculation under the shared-care formula in RCW 26.19.080. A support obligation often remains, though it is typically reduced to account for duplicated expenses in two households. The disparity in the incomes of the parents has a significant impact on whether deviation from a 50/50 custody will be granted and to what degree.
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Yes, but the court must make written findings justifying the deviation under RCW 26.19.075. Deviation is granted sparingly — judges presume the guideline amount is correct. The most common reasons for seeking a deviation include nonrecurring income, residential schedule, and support paid for children from other relationships.
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The calculator uses both parents’ combined monthly net income and the number of children to look up a base obligation on the statutory schedule in RCW 26.19.020. Each parent is then responsible for their proportional share of that amount based on their percentage of the combined income.
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