CO-288 Denial Code: Referral Absent

The official definition

“Referral absent”

That is the verbatim definition of CARC 288 from the X12 Claim Adjustment Reason Code set, the standardized codes every insurer uses on EOBs and remittance advices. The letters in front of the number are the group code. CO: Contractual Obligation: an adjustment between the provider and the insurer. An in-network provider should not bill you for CO amounts.

What it means in plain English

Your plan required a referral (typically from your primary care provider) before you saw this specialist, and no referral was on file when the claim processed. Often the referral exists and simply never made it onto the claim, which makes this one of the more fixable denials on the list.

What to check on your EOB

• Whether a referral was actually issued; ask your PCP's office for the referral number and date.
• Your plan type. Referral requirements are an HMO/POS feature; PPO plans generally don't require them.
• Whether the specialist's office was told about the referral and failed to include it on the claim.

What to do next

1. If the referral exists, have the specialist's office resubmit the claim with the referral information attached.
2. If it was never issued, ask your PCP whether they'll issue one retroactively; many plans accept backdated referrals for care that was clearly appropriate.
3. If the plan refuses retroactive referral for medically necessary care, appeal with your PCP's supporting note.

Who's responsible

Provider offices, with a push from you. Most denials carry a clear owner. Knowing whether the fix belongs to you, your doctor, or the billing office is half the battle. If it's the provider's error, you should not be paying for it.

Want the fundamentals first? Start with how to read an EOB and the 7 most common billing errors. This page is general information about standardized denial codes, not legal or medical advice.