A support modification is a court-approved change to an existing child support order. In Washington a modification requires showing a substantial change in circumstances — typically a 15% or more change in either parent's net income under RCW 26.09.170.
RCW 26.09.170 governs modification of child support orders in Washington. A substantial change in circumstances is required. Washington presumes a substantial change exists when the order would change by 15% or more based on current income.
Income changes: Either parent's income increases or decreases by 15% or more since the last order. A parent loses employment involuntarily. A parent receives a significant promotion or change in employment.
Expense changes: Childcare costs change substantially when a child starts or leaves daycare. Healthcare costs change significantly. A child develops special medical needs.
Residential changes: The residential schedule changes substantially. A child moves to a different primary parent. A child reaches age 18 or graduates high school.
A successful modification replaces the existing order with a new one. The new order is effective from the date of filing the petition in most cases — not from the date of the hearing. File promptly when circumstances change.
There is no minimum waiting period. A modification can be requested any time there is a substantial change in circumstances. However courts discourage frequent filings without meaningful changes.
Yes — a stipulated modification agreed by both parents still requires court approval and a new court order. An informal private agreement is not legally enforceable.
No. Modification is generally effective from the date the petition is filed with the court — not the date income changed. File promptly.
Use our 2026 Washington State estimator to see how these legal terms impact your support amount. All calculators are RCW 26.19 compliant.