How to Calculate Child Support in Washington State (2026 Guide)
Author
WSCSS Editorial Team
Reading Time
8 min
This is for informational purposes only. Child support orders are set by a court. Always consult a family law attorney.
Child support in Washington uses the WSCSS (Washington State Child Support Schedule) formula under RCW 26.19. Both parents' net incomes are used. To see your results, you can complete your child support worksheet online. This guide explains the full process step by step.
Table of Contents
What Is the WA Child Support Schedule?
- Established under RCW 26.19
- Income shares model
- Both parents' incomes factored in
- Reflects what parents would spend if together
Who Pays Child Support in Washington?
- Non-residential parent typically pays
- Even 50/50 custody may still require payment
- Depends on income differences
How Is Child Support Calculated?
Step-by-Step Calculation
Step 1, Calculate Each Parent's Gross Monthly Income
Include wages, salaries, tips, bonuses, self-employment, rental income, Social Security. Exclude TANF and SSI.
The Imputed Income Trap: What If a Parent Refuses to Work?
A common concern is whether a parent can intentionally quit their job or take a lower-paying position to minimize their child support obligation. In Washington, the courts look out for this. If a judge finds that a parent is voluntarily unemployed or underemployed, they will "impute" income to that parent. This means the court assigns a hypothetical income based on the parent's work history, educational background, and local earning potential. If no historical data exists, the court defaults to the state’s minimum wage for a 40-hour work week.
Step 2. Determine Net Monthly Income
Deduct: federal/state taxes, FICA, mandatory union dues, mandatory pension, court-ordered support for other children. Do NOT deduct voluntary expenses.
📥 Free Tool: Don't miss a single legal deduction.
Download our 2026 WA Child Support Document Checklist (PDF) to ensure you gather every paystub, tax return, and expense receipt required for your Worksheet Wizard.
- ✓ Proof of Income (6 months paystubs)
- ✓ Tax Records (2 years returns/W-2s)
- ✓ Self-Employment Records (YTD P&L)
- ✓ Mandatory Deductions (Union, pension)
- ✓ Health Insurance (Premium proof)
- ✓ Special Expenses (Daycare/Medical)
Step 3 — Add Both Net Incomes Together
This gives the Combined Monthly Net Income used in the WSCSS table.
Step 4. Look Up the Basic Support Obligation
Find the income row and number-of-children column in the WSCSS table.
Step 5. Calculate Each Parent's Proportional Share
Each parent's net ÷ combined net × BSO = their share. Non-residential parent's share = transfer payment.
Step 6 — Add Additional Expenses
Child care, health insurance premiums, and extraordinary medical expenses are split proportionally on top of the base amount.
Sample Income & Support Table (1 Child)
| Combined Net Monthly Income | BSO (1 Child) | BSO (2 Children) | BSO (3 Children) |
|---|---|---|---|
| $1,000 | $252 | $349 | $396 |
| $2,000 | $401 | $556 | $631 |
| $3,000 | $515 | $713 | $809 |
| $4,000 | $612 | $847 | $961 |
| $5,000 | $697 | $966 | $1,096 |
| $6,000 | $770 | $1,067 | $1,210 |
| $7,000 | $844 | $1,169 | $1,326 |
| $8,000 | $908 | $1,258 | $1,426 |
| $10,000 | $1,013 | $1,404 | $1,591 |
These are approximate figures. Use the official WSCSS table or our calculator for accurate numbers.
When Can Child Support Be Reviewed or Changed?
In Washington, child support orders are not permanent. They can be modified when life circumstances change significantly. Use the table below for a quick glance at the legal requirements for a review.
| Reason for Modification | Time Frame Allowed | Requirement |
|---|---|---|
| Standard Review | Every 24 months | Requires showing a substantial change in economic circumstances or income. |
| Child Age Change | At any time | Automatically triggered when a child turns 12 and moves to the higher-cost bracket. |
| Emergency / Severe Change | Less than 12 months | Requires proving an unprecedented, involuntary hardship (e.g., permanent medical disability). |
When Can Courts Deviate from the Formula?
Courts can deviate when standard amount would be unjust. Reasons include:
- Significant residential time with non-custodial parent
- Special needs of the child
- Tax benefits received by a parent
- Non-recurring income (bonuses, inheritances)
- Income of a new spouse (considered but not directly counted)
Any deviation must be written in the order with explanation.
What happens if child support payments are late?
The Cost of Late Payments: Washington’s 12% Arrears Penalty
If a parent falls behind on court-ordered child support in Washington, the financial consequences mount quickly. Under state law, child support arrears accumulate a strict 12% annual interest rate (calculated at 1% per month). This interest is mandatory and cannot be waived by the other parent or easily reduced by a judge. Furthermore, the Division of Child Support (DCS) can enforce collection through automatic wage garnishments, federal tax refund intercepts, and passport denials. If your financial situation changes, it is critical to file for an official modification immediately rather than just letting payments lapse.
Keep Reading
Related Washington Child Support Guides
2026 Washington State Child Support Guidelines: The Complete Handbook
Filing for Child Support in King County: A Step-by-Step Guide
Understanding the $2,394 Self-Support Reserve (SSR) in 2026
Frequently Asked Questions About Washington Child Support
Not automatically. Even with equal residential time, if one parent earns significantly more, they may still owe support. The WSCSS formula accounts for shared custody, often reducing but not eliminating support.
Gross income minus legitimate business expenses. Courts can impute income if a parent appears underemployed or hiding income.
Calculate Your Exact Child Support
Get an immediate estimate based on the 2026 Washington State Economic Tables. Our tool accounts for the expanded $50,000 threshold and the $2,394 Self-Support Reserve.
Calculate Your Child SupportWSCSS Editorial & Legal Team
Our calculations and guides are rigorously audited by family law advocates and technical developers to ensure compliance with RCW 26.19 and the latest 2026 economic table updates. We maintain a strict editorial protocol based on official AOC mandatory forms and WAC guidelines.
Transparency Disclosure: WSCSS is an independent resource center. We are not a government agency or a law firm. Our calculations are provided for educational and estimation purposes based on the latest 2026 guidelines.
All WSCSS insights are reviewed for compliance with RCW 26.19.065 and official Washington State guidelines. Our team cross-references all data with official AOC publications.