Child Support Modification in Washington State

When You Can Request a Modification

Washington allows child support modifications under RCW 26.09.170 through several routes:

A substantial change in circumstances. Either parent can seek a modification when circumstances have substantially changed, including a job loss, a significant raise, a change in the parenting schedule, a child's medical needs increasing, or the addition of other dependents.

Statutory review routes based on the order's age. After one year, a court may modify support without a substantial-change showing when the statutory conditions are met, including severe economic hardship. After 24 months, either party may seek an adjustment based on changes in income or the economic table without showing a substantial change. The 15%, $100, and $2,400 thresholds belong to DCS review criteria, not a blanket court-petition rule.

The Washington Child Support Worksheet

Every child support calculation in Washington uses the standardized Washington State Child Support Worksheets. The resulting support order is entered on Form FL All Family 130. The worksheets take both parents' gross monthly incomes, apply the Washington State Child Support Schedule, and produce a presumptive support amount based on the combined income and the number of children.

Key inputs that affect the calculation:

Gross income includes wages, salaries, commissions, bonuses, self-employment income, rental income, and most government benefits. It does not include public assistance payments like TANF or SSI.

Deductions from gross income are limited to mandatory items: federal and state income taxes (at the single filing rate), FICA, mandatory union dues, mandatory pension contributions, and existing court-ordered support for other children.

Residential schedules may affect the support calculation. Use the current Washington State Child Support Schedule and the court order to determine whether any applicable adjustment applies.

Health insurance premiums for the children are added to the base support amount and split proportionally between the parents based on their income shares.

Filing the Modification

You have two paths depending on whether the Division of Child Support (DCS) is already involved in your case.

If DCS is managing your case — meaning you receive TANF, have requested non-assistance enforcement, or the other parent's wages are being garnished through DCS — you can request a review and adjustment directly through DCS. DCS applies its review criteria; for a court-based order, it may refer a qualifying case to the county prosecutor, who decides whether to bring the modification action. There is no court filing fee for a DCS-initiated review.

If DCS is not involved — a "non-assistance" case where support is paid directly between parents — you file a Petition to Modify Child Support in the Superior Court that entered the original order. You complete updated Child Support Worksheets, attach proof of both parents' current income, and pay the court filing fee (typically $30 to $60 depending on the county).

Either way, the other parent gets notice and an opportunity to respond. If both parents agree on the new amount, the court can enter an agreed modification order without a hearing. If there is a dispute, the court schedules a hearing where both parents present evidence of their income and expenses.

Non-Assistance Enforcement

If the other parent owes child support and you are not receiving TANF, you can still open a non-assistance enforcement case with DCS. This gives you access to DCS enforcement tools — wage garnishment, tax refund interception, license suspension, and passport denial — without needing to hire a private attorney.

To open a non-assistance case, you apply through DCS and provide your existing court order and the other parent's identifying information. DCS retains a $35 annual fee in qualifying non-assistance cases when it collects and disburses at least $550 in a federal fiscal year and the person entitled to receive support has never received TANF, Tribal TANF, or AFDC as the custodian of minor children. Once the case is open, DCS handles collections and forwards payments to you through the Washington State Support Registry (WSSR).

When Modification Takes Effect

A modified child support order generally applies only to installments accruing after the petition or motion is filed, not to support that came due before filing. This matters if months pass between filing and the hearing — the adjustment can affect the installments accruing during that period, and any overpayment or underpayment is credited or owed accordingly.

This filing-date rule is why timing matters. If your income dropped significantly, file the modification petition as soon as you meet the eligibility criteria. Waiting three months means three months of support at the old (higher) rate that you cannot recover.

The Washington After-Divorce Checklist includes the full child support and WSSR enrollment sequence alongside every other post-decree administrative task.

See more Washington guides →