Updated for 2026 guidelines
Washington Child Support Arrears Calculator 2026
Washington has one of the steepest support interest rates in the country on paper: 12 percent a year. It also has a practice gap most pages skip: the state collection agency does not run that interest on its ledgers. This calculator shows the statutory figure and tells you exactly what it is and is not.
Reviewed by SupportDecode Editorial Team Page content reviewed Sources Methodology Update log
Estimate a Washington arrears balance with interest
Estimated arrears with interest: $5,600.00
Interest of $600.00 at 12% simple per year (RCW 4.56.110(2) (12 percent on judgments for unpaid child support)).
| Line item | Amount |
|---|---|
| Arrears principalRCW 4.56.110 (interest on judgments; subsection (2): judgments for unpaid child support bear interest at 12 percent) (Washington State Legislature (app.leg.wa.gov)) | $5,000.00 |
| Simple interest at 12% per year for 12 month(s) (RCW 4.56.110(2) (12 percent on judgments for unpaid child support))The 12 percent statutory rate attaches to support judgments, and each unpaid installment becomes a judgment as it falls due. In practice the Division of Child Support does not routinely calculate or collect this interest administratively: reducing the interest to a collectible figure generally takes judicial action, and DCS agency practice on interest is official-confirmation-required. Treat the computed interest as what a court could award under RCW 4.56.110(2), not as a balance DCS is already carrying.RCW 4.56.110 (interest on judgments; subsection (2): judgments for unpaid child support bear interest at 12 percent) (Washington State Legislature (app.leg.wa.gov)) | $600.00 |
| Arrears principal plus interestRCW 4.56.110 (interest on judgments; subsection (2): judgments for unpaid child support bear interest at 12 percent) (Washington State Legislature (app.leg.wa.gov)) | $5,600.00 |
Assumptions
- Accrual period expressed as 12 month(s); partial months prorate.
Estimate only. The court or state agency calculation controls.
Washington arrears interest under RCW 4.56.110(2) (12 percent on judgments for unpaid child support); rules last reviewed 2026-08-08.
How arrears and interest work in Washington
Arrears are support installments that came due and went unpaid. In Washington each installment is treated as a judgment when it falls due, which matters because the judgment interest statute is where the interest rate lives. The Division of Child Support keeps the payment ledger for cases in its system; for court-only cases, the order and the court record define the debt.
The rate is statutory and specific. RCW 4.56.110(2) provides that all judgments for unpaid child support that have accrued under a superior court order or an administrative order bear interest at 12 percent. It is simple interest; the statute has no compounding provision. A citation note for anyone checking our work: older sources cite subsection (3), but the 2018 restructuring of RCW 4.56.110 moved the child support provision to subsection (2), where it sits today.
Now the practice gap. DCS does not routinely calculate, add, or collect this interest on its administrative ledger. Getting 12 percent interest actually charged generally takes judicial action: a party asks the court to determine the accrued interest and reduce it to a collectible figure. So there are usually two numbers in a Washington arrears case: the principal DCS is enforcing, and the larger principal-plus-interest figure a court could award if asked. This calculator computes the second; your DCS statement shows the first.
The principal itself is durable. Washington cannot retroactively modify vested installments, enforcement tools run from wage withholding and license suspension to liens and contempt, and a 10-year collection window on each installment (extendable) keeps old debt alive far longer than most private debts.
- Interest rate
- 12 percent per year, simple, on judgments for unpaid child supportsource
- Statute
- RCW 4.56.110(2); the child-support rate moved here from (3) in the 2018 restructuringsource
- When interest attaches
- Each unpaid installment is treated as a judgment as it falls duesource
- Agency practice
- DCS does not routinely assess this interest; charging it generally takes judicial actionsource
How to use this estimate
Enter the unpaid principal and how many months it has been outstanding. The tool applies 12 percent simple annual interest to show what the statute supports, alongside the principal.
Read the result as what a court could award under RCW 4.56.110(2), not as a balance the state is already carrying. If your DCS statement shows principal only, that is normal: the agency enforces the installments and leaves interest to the courts.
A single-rate estimate is rough by nature. Real arrears accrue installment by installment, each earning interest from its own due date, and payments land against the ledger over time. Treat the output as scale, and get the official balance from a DCS account statement or the court record before making decisions.
What this estimate includes
- The unpaid principal you enter
- Simple interest at the statutory 12 percent annual rate for the period you enter
- The distinction between the DCS-enforced principal and court-awarded interest, stated plainly
What it leaves out
- Installment-by-installment accrual from each due date; this is a single-period estimate
- Payment histories, intercepted refunds, and DCS ledger adjustments
- Interest another state added before a case transferred; that interest generally survives the move
- Current support still accruing under the order
Washington arrears FAQs
Does Washington charge interest on child support arrears?
The statute does; the agency mostly does not. RCW 4.56.110(2) sets 12 percent annual interest on judgments for unpaid child support, and each missed installment becomes a judgment when it falls due. But the Division of Child Support does not routinely compute or collect that interest administratively, so the interest typically exists as a legal entitlement until someone asks a court to fix the amount.
Is the 12 percent simple or compound?
Simple. The statute states a rate and nothing about compounding, so interest accrues on the unpaid principal only, not on accumulated interest. On $10,000 of principal, that is $1,200 a year, every year it goes unpaid, if a court is asked to award it.
How do I actually get the interest added to what I am owed?
Generally through the court: a motion to determine arrears and accrued interest, or an action reducing the debt to a single judgment with the interest computed. Bring the payment ledger, because the math runs installment by installment from each due date. Once fixed in a judgment, the amount keeps earning 12 percent and DCS can enforce the total.
Why does my DCS statement show no interest?
Because DCS enforces the support ledger, not the judgment interest statute. Its statements track installments charged and payments received. That does not erase the interest the statute provides; it means nobody has reduced it to a figure the agency can collect. If interest matters in your case, the courthouse is the venue.
Can Washington back support be reduced or forgiven?
Vested installments cannot be retroactively modified; a change reaches back only to the filing of the modification petition. Debt assigned to the state for public assistance can sometimes be compromised through DCS conference board or hardship processes. Support owed to the other parent belongs to them, and only they can agree to take less, including any interest a court has fixed.
How long can Washington collect arrears?
A long time. Each installment can generally be enforced for 10 years after the youngest child covered by the order turns 18, and judgments can be extended. Combined with the 12 percent rate available on request, waiting out a Washington support debt is a poor strategy.
Official sources
Official sources last verified: .
- RCW 4.56.110 (interest on judgments; subsection (2): judgments for unpaid child support bear interest at 12 percent)
Washington State Legislature (app.leg.wa.gov) Last checked
Reviewed by SupportDecode Editorial Team Page content reviewed Sources Methodology Update log
Changelog: page first published with the 12 percent judgment-interest rule and the agency-practice honesty note. Material changes are dated in the update log.