Net monthly income is gross income after subtracting mandatory deductions including federal and state income taxes, FICA, mandatory union dues, required pension contributions, and state insurance premiums. The 2026 economic table uses net income not gross income.
RCW 26.19.071(5): The following expenses shall be deducted from gross monthly income to calculate net monthly income: federal and state income taxes, FICA, mandatory pension plan payments, mandatory union or professional dues, mandatory state deductions, state industrial insurance premiums, court-ordered maintenance paid, voluntary retirement contributions up to $5,000 per year, and normal business expenses for self-employed persons.
Start with gross monthly income (Line 1g)
Subtract these mandatory deductions:
2a: Federal and state income taxes actually owed
2b: FICA — Social Security 6.2% + Medicare 1.45%
2c: Mandatory state deductions (PFML, LTC)
2d: State industrial insurance premiums
2e: Mandatory union or professional dues
2f: Required pension plan payments
2g: Voluntary retirement up to $416/mo max
2h: Court-ordered maintenance paid
2i: Normal business expenses if self-employed
Result = Net Monthly Income (Line 3)
Net income is the foundation of the entire calculation. A higher net income means a higher combined income which means a higher table value. It also means a larger income share percentage if your net income is proportionally higher than the other parent's.
Taxes actually owed — not the withholding amount on your pay stub. Use your prior year tax return divided by 12 to estimate monthly tax liability if your income is similar.
Up to $5,000 per year ($416/mo) may be deducted if you have a consistent pattern of contributions in the year before the support order was established.
Use a monthly average. Divide annual total income by 12. For biweekly pay multiply by 26 then divide by 12.
Use our 2026 Washington State estimator to see how these legal terms impact your support amount. All calculators are RCW 26.19 compliant.