CO-136 denial code
Failure to follow the prior payer's coverage rules
How to fix it
Establish what the primary required, correct with the primary first where possible, then rebill the secondary.
How to prevent it
Resolve primary adjudication fully before billing secondary; a secondary claim inherits the primary's problems.
In practice
A primary payer denies a service for lack of authorisation. The practice bills the secondary, which returns CO-136 — the primary's coverage rules were not followed, so the secondary will not step in.
Secondary coverage is not an alternative to primary coverage. It sits behind it and generally follows its determinations, which means a problem unresolved with the primary is a problem the secondary inherits rather than cures.
The work belongs with the primary. Resolve the authorisation issue there, obtain a corrected adjudication, and only then rebill the secondary with the updated remittance attached.
What sits behind it
The temptation to skip to the secondary when the primary denies is understandable and almost always wasted effort. Most secondary contracts explicitly condition payment on the primary having been billed correctly, so the second claim fails for the same underlying reason as the first.
Sequencing also protects the filing deadline. Secondary filing windows typically run from the primary's adjudication date rather than the date of service, so resolving the primary first both fixes the substance and restarts the clock in your favour.
The related codes divide the same ground. CO-196 means the secondary followed the primary's coverage determination, CO-276 that services denied by the primary are not covered here, and CO-228 that an information request to a previous payer went unanswered. All three point back to the same place.
Related codes
Terms used here — Coordination of Benefits · Denial · Timely Filing
How we handle it — Denial Management · AR Management · Claims Management
Primary sources
The rules behind CO-136, at the bodies that publish them.
- 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 Benefit Policy Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — What Medicare covers and under what conditions, as distinct from how a claim is processed. The starting point for any coverage or medical necessity question.
- Advance Beneficiary Notice of Noncoverage (ABN) (opens in a new tab)
Centers for Medicare & Medicaid Services — The form and the rules for issuing it. Whether a non-covered service can be billed to the patient usually turns on whether a valid ABN was obtained beforehand.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-136
Rarely, and only where the secondary's contract permits it. Most condition payment on the primary having been billed and adjudicated correctly, so a claim carrying an unresolved primary denial will fail at the secondary for the same underlying reason.
It usually saves it. Secondary filing windows generally run from the primary's adjudication date rather than the service date, so resolving the primary produces a corrected remittance and restarts the secondary clock at the same time.
The corrected primary remittance showing the revised adjudication, with the coordination of benefits data on the claim matching it at line level. Sending the original denial alongside a narrative explanation is considerably weaker than sending the corrected adjudication itself.
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