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CO-W1 Denial Code (Deactivated): WC Fee Schedule Adjustment

CO-W1 meant a workers' compensation payer reduced the bill to the amount allowed by the jurisdiction's fee schedule. X12 deactivated it and its notes direct payers to code P12.

X12 deactivated CARCW1 on July 1, 2014. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Quick facts

Code
CO-W1 (CARC W1)
Status
Deactivated StoppedJuly 1, 2014 (in use since February 29, 2000).
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The reduction to the state fee schedule was a provider adjustment, and state rules generally bar billing the injured worker for it.
Official description
Workers' compensation jurisdictional fee schedule adjustment. Note: If adjustment is at the Claim Level, the payer must send and the provider should refer to the 835 Class of Contract Code Identification Segment (Loop 2100 Other Claim Related Information REF). If adjustment is at the Line Level, the payer must send and the provider should refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment information REF) if the regulations apply.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-W1 meant

The W-series held workers’ compensation codes, and W1 was the workhorse among them. When a state sets maximum fees for treating injured workers, the carrier reduces each bill to the fee schedule amount. CARC W1 reported that reduction and pointed to the 835 reference fields where the payer should identify the governing regulation.

What replaced it

X12’s note says to use code P12. CO-P12 now reports the workers’ compensation jurisdictional fee schedule adjustment within the property and casualty P-series. If the reduction comes from other regulations or payment policies, carriers use CO-P13. When the billed service is not on the schedule and a comparable one is used, the code is CO-P18.

If you still see CO-W1

Older workers’ compensation remittances will show it. Check the allowed amount against the state’s fee schedule for that date of service, including any modifiers or geographic factors the state applies. If the carrier used the wrong rate, request reconsideration under the state’s billing dispute process. Otherwise, post the reduction as an adjustment rather than billing the worker.

  • CO-P12 (Workers' compensation jurisdictional fee schedule adjustment.): Named replacement: workers' compensation jurisdictional fee schedule adjustment.
  • CO-P13 (Payment reduced or denied based on workers' compensation jurisdictional regulations or payment policies, use only if no other code is applicable.): Reduced or denied under workers' compensation regulations or payment policies.
  • CO-P18 (Procedure is not listed in the jurisdiction fee schedule.): Procedure not in the jurisdiction fee schedule; allowance made for a comparable service.

CO-W1 FAQ

What is a jurisdictional fee schedule?

Most states set maximum payment amounts for medical care under workers' compensation. Payers reduce bills to those amounts, and the reduction was reported with CO-W1.

Is W1 the most common workers' comp code?

Fee schedule reductions are routine on workers' compensation bills, much like contractual adjustments on health claims. Today they carry CARC P12.