Washington law limits child support to 45% of a parent's net monthly income for all their biological or legal children combined. Courts may exceed this cap only for good cause including substantial wealth or special needs of the children under RCW 26.19.065.
RCW 26.19.065(1): No parent's child support obligation owed for all of their biological or legal children may exceed 45% of their net income except for good cause shown. Good cause includes substantial wealth, children with special needs, larger families, and daycare expenses.
The cap applies to the total obligation for ALL of a parent's children across all cases not just the children in the current case. Understanding this term is important when completing your child support calculation. Use our worksheet calculator to see how this applies to your case.
Line 18 of the WSCSS worksheet calculates 45% of each parent's net income as an informational figure for the court to review.
If the total obligation across all cases exceeds 45% the court considers whether to apply the limitation before determining the best interests of the children.
The cap prevents child support from consuming an unreasonable portion of a parent's income when they have children from multiple relationships. Courts must consider the best interests of all children affected — not just those in the current case.
No. The court must consider whether to apply it after reviewing the best interests of the children and circumstances of both households. It is a ceiling not an automatic reduction.
Use our 2026 Washington State estimator to see how these legal terms impact your support amount. All calculators are RCW 26.19 compliant.