CO-243 denial code
Services not authorized by network or primary care providers
How to fix it
Obtain retroactive authorisation where the plan permits, or appeal.
How to prevent it
Identify gatekeeper plans at scheduling and confirm authorisation before the visit.
In practice
A patient on a gatekeeper plan attends a specialist without the primary care physician's authorisation. The specialist bills and the claim returns CO-243.
The plan requires the designated primary care provider to authorise specialist care, and without that authorisation the service is treated as unauthorised regardless of clinical appropriateness.
Many plans allow a retroactive authorisation within a defined window if the primary care physician will issue one. That route is faster and more reliable than an appeal, and should be tried first.
What sits behind it
The structural unfairness here is familiar: the specialist absorbs a denial caused by a step that belonged to another practice. Because payment flows to the rendering provider, the rendering provider carries the loss.
That makes confirmation at scheduling the only real defence. Verifying that authorisation exists when the appointment is booked costs minutes; discovering its absence afterwards costs the encounter and creates a patient conversation nobody wants.
Related codes divide the same territory. CO-288 reports an absent referral, CO-287 an exceeded one, and CO-38 the broader network and referral failure. Reading which arrived tells you precisely what to request from the primary care office.
Related codes
Terms used here — Prior Authorization · Out-of-Network · Denial
How we handle it — Prior Authorization · Eligibility Verification · Denial Management
Primary sources
The rules behind CO-243, 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-243
Often, within a window the plan defines, provided the primary care physician will issue it. That route is faster and more reliable than appealing, so it should be the first call rather than the fallback.
Because payment flows to the rendering provider, so the loss lands on the practice that delivered the care rather than the one that failed to authorise it. Confirming authorisation at scheduling is the only protection available.
The eligibility response usually identifies a designated primary care provider, which is the clearest indicator. Health maintenance organisation and point-of-service products are the common structures; preferred provider plans rarely require gatekeeper authorisation.
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