Child Support in Washington

Free calculator, modification rules, arrears interest, and 50/50 custody guide for Washington — 2026.

Child Support Calculator

Estimate payments using Washington's Income Shares

Modification Checker

Does your income change qualify?

Arrears Calculator

Past-due support with 12% interest

50/50 Custody Guide

Does equal custody eliminate support?

Washington Child Support Facts — 2026

Formula modelIncome Shares

Income basisBoth parents' income

Support ends at age18

Modification threshold25% income change

Arrears interest rate12% per year

Income cap$50,000/month

Official agencyWashington Child Support Agency ↗

Washington uses Income Shares. The Economic Table covers combined monthly income from $2,200 to $50,000 (2026). Self-support reserve: $2,394/month.

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