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CO-P16 Denial Code: Provider Not Authorized for WC Care

CO-P16 means the medical provider isn't authorized or certified to treat injured workers in this workers' compensation jurisdiction. Some states require providers to register, be certified, or belong to an approved network before workers' comp will pay them.

Quick facts

Code
CO-P16 (CARC P16)
Status
Active In use since November 1, 2013.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): One of two groups X12 allows. The provider absorbs the amount; state rules generally prevent billing the injured worker.
  • OA (Other Adjustment): The other allowed group, used when the payer doesn't assign the amount to either party.
Official description
Medical provider not authorized/certified to provide treatment to injured workers in this jurisdiction. To be used for Workers' Compensation only. (Use with Group Code CO or OA)
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-P16 means

CARC P16 says medical provider not authorized or certified to provide treatment to injured workers in this jurisdiction. X12 limits it to workers’ compensation and allows only group codes CO or OA. It replaced deactivated CARC W5.

Workers’ comp systems are state-run, and several states control which providers can treat injured workers. Depending on the state, that may mean registering with the workers’ comp agency, completing training or certification, or joining an approved medical provider network. A provider who isn’t authorized under those rules may be denied payment with CO-P16 even when the treatment was appropriate.

This is similar to CO-B7 for health plans, but the requirement comes from state workers’ comp law rather than a payer’s credentialing.

Common causes

  • Provider not registered or certified with the state workers’ comp program.
  • Certification expired or not renewed.
  • Provider outside the required network, such as a Medical Provider Network.
  • Treating provider changed without following the state’s rules for changing physicians.
  • Out-of-state provider treating a worker whose claim is under another state’s jurisdiction.

How to fix it

  1. Confirm the jurisdiction of the claim and that state’s provider requirements.
  2. Check your status with the state agency or network.
  3. If you’re authorized, send proof to the payer and request reprocessing.
  4. If you’re not, apply for authorization and ask whether it can apply to past dates. Many states don’t allow that.
  5. Refer the worker to an authorized provider for continuing care if needed.
  6. Don’t bill the injured worker unless state law allows it.

How to prevent it

  • Verify authorization requirements for each state before accepting workers’ comp patients.
  • Track certification and network renewal dates.
  • Confirm with the carrier that you can treat the worker before the first visit.
  • Keep enrollment records organized. See provider enrollment denials.

Specialty notes

Specialists receiving referrals for injured workers should confirm authorization before accepting the case, since the referring provider’s authorization doesn’t cover them.

Remark codes that may appear with CO-P16

  • N612 (Medical provider not authorized/certified to provide treatment to injured workers in this jurisdiction.): The medical provider isn't authorized or certified to treat injured workers in this jurisdiction.
  • N761 (This provider is not authorized to receive payment for the service(s).): This provider isn't authorized to receive payment for the service.
  • CO-W5Deactivated (Medical provider not authorized/certified to provide treatment to injured workers in this jurisdiction. (Use with Group Code CO or OA)): The deactivated code that CARC P16 replaced.
  • CO-B7 (This provider was not certified/eligible to be paid for this procedure/service on this date of service.): The provider wasn't certified or eligible on the date of service, the general version outside workers' comp.
  • CO-P25 (Payment adjusted based on Medical Provider Network (MPN).): Payment adjusted based on a Medical Provider Network.
  • CO-P17 (Referral not authorized by attending physician per regulatory requirement.): Referral not authorized by the attending physician.

CO-P16 FAQ

Why do states certify workers' comp providers?

Some states require provider registration, certification, or network participation to control quality and costs in workers' comp. Requirements differ widely by state.

What if the injured worker chose me as their provider?

Choice-of-provider rules vary. In some states the employer or carrier directs care initially; in others the worker chooses from a network or list. If you aren't authorized, payment may be denied even if the worker chose you.

How do I fix CO-P16?

Check the state's provider requirements. If you're authorized, send proof to the payer. If not, apply for certification or network membership and ask whether the state allows retroactive payment.

Is CO-P16 used outside workers' comp?

No. X12 limits it to workers' compensation.

Does authorization in one state cover another?

No. Each workers' comp jurisdiction sets its own provider rules, so authorization in one state doesn't carry over to claims under another state's law.