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CO-191 Denial Code (Deactivated): Not Work-Related

CO-191 meant a workers' compensation carrier found the injury or illness was not work-related, so it was not liable. X12 deactivated it and its notes direct payers to code P2.

X12 deactivated CARC191 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.

Code: CO-191 (CARC 191)
Status: Deactivated StoppedJuly 1, 2014 (in use since October 31, 2005).
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): The workers' compensation carrier declined liability; the provider needed to pursue other coverage.
Official description: Not a work related injury/illness and thus not the liability of the workers' compensation carrier Note: If adjustment is at the Claim Level, the payer must send and the provider should refer to the 835 Insurance Policy Number Segment (Loop 2100 Other Claim Related Information REF qualifier 'IG') for the jurisdictional regulation. 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)
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-191 meant

CARC 191 was a workers’ compensation code. The carrier reviewed the claim and concluded that the injury or illness did not arise from the patient’s employment, so the employer’s workers’ compensation coverage would not pay. The code’s text also told providers where on the 835 to find the jurisdictional regulation behind the decision.

What replaced it

X12’s note says to use code P2. CO-P2 carries the same meaning in the property and casualty P-series, which now houses workers’ compensation codes. When a claim is found non-compensable for other reasons, carriers use CO-P4. The mirror-image health plan code is OA-19, used when a health plan says the injury is work-related.

If you still see CO-191

It can appear in older workers’ compensation files. Bill the patient’s health plan and include the carrier’s denial, since health plans often deny first for suspected work injuries. If the patient is contesting the finding with the workers’ compensation board, keep the claim open and track the outcome, as the liable payer may change.

CO-P2 (Not a work related injury/illness and thus not the liability of the workers' compensation carrier): Named replacement: not a work-related injury or illness, not the workers' compensation carrier's liability.
CO-P4 (Workers' Compensation claim adjudicated as non-compensable.): Workers' compensation claim adjudicated as non-compensable.
OA-19 (This is a work-related injury/illness and thus the liability of the Worker's Compensation Carrier.): The opposite finding from a health plan: the injury is work-related and belongs to workers' compensation.

CO-191 FAQ

Where should the claim go after a CO-191 or P2?

Usually to the patient's health plan, with a copy of the workers' compensation denial. If the injury involved an auto accident or another party, that carrier may be responsible instead.

Can the finding be disputed?

Workers' compensation compensability disputes are typically handled through the state's workers' compensation system. Providers usually coordinate with the patient and employer rather than appeal alone.

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