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CO-Y1 Denial Code (Deactivated): MPC/PIP Denial

CO-Y1 meant an auto insurer denied payment based on Medical Payments Coverage or Personal Injury Protection jurisdictional regulations or payment policies, when no other code applied. X12 deactivated it and its notes direct payers to code P21.

X12 deactivated CARCY1 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-Y1 (CARC Y1)
Status: Deactivated StoppedJuly 1, 2014 (in use since September 30, 2012).
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): The denial stayed with the provider under the applicable auto coverage rules.
Official description: Payment denied based on Medical Payments Coverage (MPC) or Personal Injury Protection (PIP) Benefits jurisdictional regulations or payment policies, use only if no other code is applicable. 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') if the jurisdictional regulation applies. 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. To be used for P&C Auto only.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-Y1 meant

The Y-series held codes for auto insurance medical coverage, a branch of property and casualty. CARC Y1 was the denial code for Medical Payments Coverage and Personal Injury Protection claims, used when the carrier refused payment under state regulations or its payment policies and no more specific code fit.

What replaced it

X12’s note says to use code P21. CO-P21 now reports denials under MPC or PIP rules. When the carrier reduces rather than denies, it uses CO-P22. Denials under liability coverage use CO-P27.

If you still see CO-Y1

It is found only on older auto claims. Ask the adjuster for the specific rule, such as exhausted PIP limits, a missed deadline, or an excluded provider type. If the auto benefits are exhausted or do not apply, bill the next responsible payer with the denial as proof.

CO-P21 (Payment denied based on the Medical Payments Coverage (MPC) and/or Personal Injury Protection (PIP)): Named replacement: payment denied based on MPC or PIP jurisdictional regulations or payment policies.
CO-P22 (Payment adjusted based on the Medical Payments Coverage (MPC) and/or Personal Injury Protection (PIP)): Payment adjusted, rather than denied, under MPC or PIP rules.
CO-P27 (Payment denied based on the Liability Coverage Benefits jurisdictional regulations and/or payment policies.): Payment denied based on liability coverage benefits rules.

CO-Y1 FAQ

What are MPC and PIP?

Medical Payments Coverage and Personal Injury Protection are parts of auto insurance policies that pay medical costs after an accident. Rules for PIP in particular vary by state.

Where does the claim go after an auto denial?

Often to the patient's health plan, with the auto denial attached, or to another liable carrier. The right order depends on state law and the policies involved.

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