A proportional share is each parent's percentage of the combined net income. This percentage determines each parent's share of the basic obligation and all extraordinary expenses including healthcare and daycare.
RCW 26.19.080(1): The basic child support obligation shall be allocated between the parents based on each parent's share of the combined monthly net income. Line 6 of the WSCSS worksheet records each parent's proportional share.
Formula: Parent share % = Parent net income ÷ Combined net income Understanding this term is important when completing your child support calculation. Use our worksheet calculator to see how this applies to your case.
Example: P1 net: $7,000 / P2 net: $3,000, Combined: $10,000
P1 share: $7,000 ÷ $10,000 = 70%, P2 share: $3,000 ÷ $10,000 = 30%
Both percentages must always add up to 100%.
Your proportional share percentage determines your obligation for both basic support and all extraordinary expenses. It is recalculated every time either parent's net income changes. A modification that changes income will change the proportional share percentages for both parents simultaneously.
Yes. Any substantial income change of 15% or more can trigger a modification that recalculates both parents' proportional shares and adjusts the transfer payment.
Use our 2026 Washington State estimator to see how these legal terms impact your support amount. All calculators are RCW 26.19 compliant.