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CO-P17 Denial Code: Referral Not Authorized by Attending

CO-P17 means a property and casualty payer denied the service because the referral wasn't authorized by the attending physician, as state regulations require. In workers' comp especially, specialists and therapists may need a referral from the treating physician.

Quick facts

Code
CO-P17 (CARC P17)
Status
Active In use since November 1, 2013.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The provider absorbs the amount, and state rules generally prevent billing the claimant.
Official description
Referral not authorized by attending physician per regulatory requirement. To be used for Property and Casualty only.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-P17 means

CARC P17 says referral not authorized by attending physician per regulatory requirement. X12 limits it to property and casualty claims. It replaced deactivated CARC W6.

Some state P&C rules, particularly in workers’ comp, route care through an attending or primary treating physician. Specialists, therapists, and other providers can only be paid if that physician authorized the referral. When the payer can’t find a valid referral from the attending physician, the bill is denied with CO-P17.

This resembles a health plan’s missing referral (CARC 288), but the requirement comes from state regulation rather than plan rules, and the referral must come from a specific physician.

Common causes

  • Self-referred patient seen by a specialist or therapist without the attending physician’s order.
  • Referral from a non-attending provider, such as an urgent care clinician after the attending was designated.
  • Referral not sent to the carrier or not in its file.
  • Referral expired or didn’t cover the service or number of visits.
  • Referring provider missing from the bill (box 17 and 17b).

How to fix it

  1. Get a copy of the referral and check who issued it, its date, and what it covers.
  2. If it’s valid, send it to the carrier with the bill and request reconsideration.
  3. If it’s missing, ask the attending physician whether they will authorize the referral, and follow state rules on whether it can cover past dates.
  4. Add the referring provider to box 17 and 17b and resubmit.
  5. Don’t bill the claimant unless state rules allow it.

How to prevent it

  • Require a referral from the attending physician before scheduling workers’ comp patients.
  • Confirm the attending physician with the carrier at intake.
  • Track referral limits, such as visit counts or expiration dates.
  • Include referring provider details on every bill. See authorization and referral denials.

Specialty notes

PT, OT, chiropractic, and behavioral health providers who receive workers’ comp patients most often depend on referrals from the attending physician and are the most likely to see CO-P17.

Remark codes that may appear with CO-P17

  • N630 (Referral not authorized by attending physician.): The referral wasn't authorized by the attending physician.
  • N286 (Missing/incomplete/invalid referring provider primary identifier.): The referring provider identifier is missing or invalid.
  • CO-W6Deactivated (Referral not authorized by attending physician per regulatory requirement.): The deactivated code that CARC P17 replaced.
  • CO-288 (Referral absent): Referral absent, the general code used by health plans.
  • CO-287 (Referral exceeded): Referral exceeded.
  • CO-P16 (Medical provider not authorized/certified to provide treatment to injured workers in this jurisdiction.): The provider isn't authorized to treat injured workers in the jurisdiction.

CO-P17 FAQ

Who is the attending physician in a workers' comp case?

The primary treating physician responsible for managing the injured worker's care. Many states require referrals to specialists or therapy to come from that physician.

How do I fix CO-P17?

Get the attending physician's referral or order that covers the date of service, include the referring provider's name and NPI on the bill (box 17 and 17b), and resubmit or request reconsideration.

What if the referral came from another provider?

It may not satisfy the rule. Ask the attending physician to issue or confirm the referral, if appropriate.

Is CO-P17 used by health plans?

No. X12 limits it to property and casualty claims.

Does a referral last for the whole course of treatment?

Not always. Referrals may be limited by time, number of visits, or type of service. Check the referral's terms and request a new one before it runs out.