CO 288 denial code

Claim adjustment reason code 288. Often reported as CO 288.

No referral on file

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 288 means

The plan requires a referral for this service and none was on file, so the claim was not paid as billed.

The patient's plan needs a referral, usually from the primary care provider, before specialist or certain other services. The payer has no record of one for this patient, provider, and service.

Sometimes the referral exists but was never entered with the payer, or it named a different provider.

Group codes seen with 288

On a remittance, 288 comes after a group code. These are the ones it is most often reported with:

• CO 288 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• The specialist saw the patient without getting a referral first.
• The primary care office issued a referral but did not submit it to the payer.
• The referral named a different provider or group than the one that billed.

What to do next

1. Check with the primary care office whether a referral was issued and submitted.
2. Have the referral entered or corrected with the payer, then resubmit if retroactive referrals are allowed.
3. Add a referral check to scheduling for plans that require them.

Related codes

• 287 (reason code) Referral limit exceeded
• 197 (reason code) No prior authorization on file