How Is Child Support Calculated in Washington State?

Child support in Washington state is calculated by combining both parents’ net monthly incomes, looking up a base support amount on a statewide economic table that accounts for the number and ages of the children, and dividing that amount between the parents in proportion to what each one earns. The parent who does not have primary residential custody pays their share to the other parent, after adjustments for health insurance, daycare, and certain other expenses. The method is called the Income Shares Model, and it runs through a set of official worksheets that every case must use.¹

The Calculation, Step by Step

The worksheet math moves through five stages. First, each parent’s gross monthly income is established from pay stubs, tax returns from the previous two years, and other reliable proof for income that doesn’t appear on those documents.²

Second, allowable deductions come off each parent’s gross figure to produce net monthly income. The two net figures are then added together to produce combined monthly net income.

Third, that combined number is taken to the economic table published by the Administrative Office of the Courts. The table cross-references combined net income against the number of children and splits those children into two age brackets, 0 to 11 and 12 to 18, with higher amounts for older children.³ The table produces the basic support obligation.

Fourth, that basic obligation is divided between the parents in proportion to each parent’s share of combined net income.⁴ A parent earning 65% of the combined income is responsible for 65% of the base obligation. The custodial parent’s share is presumed to be spent on the child directly; the noncustodial parent’s share becomes the transfer payment.

Fifth, health insurance premiums for the child, uninsured medical expenses, work-related daycare, and any special child-rearing expenses are added on top and split in the same income-based proportions. Parents who pay these costs directly get a credit against their transfer payment.⁵ The number that comes out at the end is the presumptive transfer payment.

Two anchor points: the economic table is presumptive for combined monthly net income up to $50,000. Above that, a court can set support higher but must put its reasoning in writing. Below $2,200 in combined income, the obligation is set based on each household’s resources and living expenses rather than the table.¹

What Counts as Income

Washington defines gross monthly income broadly. It includes wages, salaries, commissions, bonuses, overtime, dividends, interest, trust income, pension benefits, Social Security, disability insurance, workers’ compensation, unemployment benefits, rental income, capital gains, self-employment profits, and spousal maintenance received from another relationship.² Each parent must also disclose all income and resources in their household, though only the parents’ own income feeds the basic calculation.

Several sources are excluded by statute: income from a new spouse or domestic partner, child support received from other relationships, public assistance such as TANF and SSI, food assistance, and certain overtime or second-job income earned specifically to pay down relationship debts or support arrears. The overtime exclusion is narrow. It applies only to hours beyond 40 per week, averaged over 12 months, where the extra work exists to retire a specific debt that will eventually end.²

Deductions That Produce Net Income

After gross income is set, RCW 26.19.071(5) allows these deductions to reach net income:²

Federal income tax (Washington has no traditional state income tax on wages, though its capital gains tax may apply to some parents).
FICA: Social Security at 6.2% and Medicare at 1.45%.
Mandatory pension and retirement contributions. Voluntary contributions can also be deducted on a showing of need.
Mandatory union or professional dues.
Other mandatory state deductions, including industrial insurance premiums and paid family and medical leave premiums actually paid.
Court-ordered spousal maintenance actually being paid to a former spouse.
Normal business expenses and self-employment taxes for self-employed parents.

Each parent’s net income is calculated separately before being combined.

The Ceiling and the Floor

Washington caps and floors the result. No parent’s total child support obligation across all biological or legal children can exceed 45% of that parent’s net income, unless the court finds good cause to go higher. Good cause can include substantial wealth, children with daycare or special medical needs, and larger families.⁶

At the bottom, when a parent’s monthly net income falls below 180% of the federal poverty guideline for a one-person household, the presumptive minimum is $50 per child per month. That minimum can be reduced if the parent proves it would be unjust, but the court must weigh the child’s needs and both households’ circumstances first. A related self-support reserve prevents the basic obligation (excluding healthcare and daycare) from pushing the paying parent’s income below 180% of the poverty level, except for the $50 minimum. The final transfer payment under the standard calculation cannot drop below $50 per child per month.⁵

When a Parent Is Unemployed or Underemployed

A parent who voluntarily quits a job or takes a lower-paying position to cut their support obligation does not get a free pass. Washington courts are required to impute income to a parent who is voluntarily unemployed or underemployed. The court looks at work history, education, job skills, health, age, criminal record, the local job market, and other barriers to employment.²

When earnings records are missing, a priority system assigns income. It starts with full-time pay at the parent’s current or most recent rate. If no reliable history exists, it drops to full-time minimum wage. For parents coming off public assistance, recently released from incarceration, or just out of high school, the presumption starts at 32 hours per week at minimum wage, which can be rebutted with evidence. As a last resort, the court uses the median net monthly income of full-time workers from U.S. Census data.

Courts will not impute income to a parent who is genuinely unemployable or one who is unemployed because of compliance with court-ordered reunification efforts in a dependency case. A parent already working full-time will not have extra income imputed unless the court specifically finds purposeful underemployment to avoid support.

Deviations from the Worksheet Number

The standard calculation is presumptive, not final. Either parent can ask the court to deviate up or down under the factors in RCW 26.19.075, and any deviation must be supported by written findings.⁷ The most common grounds:

Residential schedule. If the child spends significant time with the parent making the transfer payment, the obligation can be reduced to reflect the increased expenses that parent actually incurs. The court cannot grant this deviation if it would leave the receiving household unable to cover the child’s basic needs.
Nonrecurring income. Overtime, bonuses, or contract income that isn’t steady can be treated differently, with the court reviewing the prior two calendar years.
Extraordinary debt not voluntarily incurred, significant differences in living costs between households, or the special needs of a disabled child.
Hidden wealth or tax planning that masks real income. A new spouse’s or partner’s income can be considered, but only when the parent is already requesting a deviation for another reason.
Support actually paid for children from other relationships, or the extraordinary income of a child.

The worksheet math is straightforward. The actual fight in most cases is whether the inputs are honest and whether a deviation is warranted.

The Worksheets and the Estimator

Every child support determination in Washington must use the official worksheets developed by the Administrative Office of the Courts. They are completed under penalty of perjury, and the court will reject anything incomplete or altered from the standard form.³ The 2026 versions of the schedule and worksheets are posted on the Washington Courts website and reflect the higher $50,000 presumptive income cap that took effect January 1, 2026.

For a rough early estimate, the Division of Child Support publishes a free Quick Estimator that uses simplified inputs to produce a ballpark monthly figure. The tool itself warns that the real number can shift based on factors it doesn’t capture, so it is not a substitute for completing the full worksheets.⁸ Completed worksheets are filed with the local Superior Court, or with the Division of Child Support if the state agency is involved, and a copy must go to the other parent. A judge or administrative law judge reviews them and, if they meet the statutory requirements, signs them into an enforceable order.

1
Washington State Legislature. Washington Code 26.19.020 – Child Support Economic Table
2
Washington State Legislature. RCW 26.19.071 – Standards for Determination of Income
3
Washington Courts. Washington State Child Support Schedule 2026
4
Washington State Legislature. RCW 26.19.080 – Allocation of Child Support Obligation
5
Washington Courts. WSCSS Child Support Worksheets 2026
6
Washington State Legislature. RCW 26.19.065 – Standards for Establishing Lower and Upper Limits on Child Support Amounts
7
Washington State Legislature. Washington Code 26.19.075 – Standards for Deviation From the Standard Calculation
8
Washington State Department of Social and Health Services. Division of Child Support – Quick Child Support Estimator