CO-288 denial code
Referral absent
How to fix it
Obtain a retroactive referral where permitted, or appeal with evidence one existed.
How to prevent it
Confirm referral presence at scheduling for gatekeeper plans.
In practice
A patient books directly with a specialist, mentions that their doctor suggested the visit, and attends. No referral was ever transmitted, and the claim returns CO-288.
A verbal suggestion is not a referral. The plan requires a documented referral on its own record, and an informal recommendation between physician and patient does not create one.
Ask the primary care physician to issue a retroactive referral, which many plans accept within a defined window. Where a referral genuinely was issued and lost in transmission, evidence of the original issue supports an appeal.
What sits behind it
The transmission gap is a real and common cause. Referrals issued in one system and required in another can fail to arrive, and neither the referring practice nor the specialist necessarily knows until a claim denies weeks later.
Checking the plan's record at scheduling rather than trusting either practice's system is what catches this. The plan's copy is the only one that matters for payment, and it is usually visible through the provider portal.
The financial exposure sits entirely with the specialist, who neither issued nor lost the referral. That asymmetry is why the check has to happen at booking, since after the encounter every option is slower and less certain.
Related codes
Terms used here — Prior Authorization · Denial · Eligibility Verification
How we handle it — Prior Authorization · Eligibility Verification · Denial Management
Primary sources
The rules behind CO-288, at the bodies that publish them.
- CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) (opens in a new tab)
Centers for Medicare & Medicaid Services — The rule imposing prior authorization decision timelines and API requirements on impacted payers. It is the single largest scheduled change to authorization workflow this decade.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- Medicare Claims Processing Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — The operative manual for how Medicare claims must be coded, submitted, adjusted and appealed. When a payer policy and a vendor's advice disagree, this settles it.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-288
No. The plan requires a referral recorded on its own system, and a physician suggesting a specialist to a patient does not create one. Patients frequently believe they were referred when nothing was transmitted, which is why the plan's record is the only reliable check.
That happens more often than expected, particularly where the referring and receiving practices use different systems. Evidence that the referral was issued — a screenshot, a system record, a letter from the referring practice — supports an appeal on that basis.
In the plan's own record, usually through the provider portal, at the point of booking. Neither practice's internal system proves the plan holds it, and the plan's copy is the only one that determines payment.
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