CO-167 shows up looking like a single problem, but it is three. The official CARC text reads: "This (these) diagnosis(es) is(are) not covered, missing, or are invalid." A missing code needs a corrected claim. An invalid code usually means an expired ICD-10. A non-covered diagnosis may need a medical-necessity argument or a patient-responsibility conversation. Getting those mixed up wastes time. Read the RARC on the ERA line before you decide how to respond.
What CO-167 means
- CO stands for Contractual Obligation. The adjustment is a contractual matter between you and the payer; you cannot balance-bill the patient for the CO-167 amount.
- 167 flags a diagnosis code problem: the code was absent, not recognized as valid, or not a covered benefit under the patient's plan.
CO-167 is not a clinical determination in the same way a CO-50 medical-necessity denial is. Most of the time it is an administrative or coding issue that a corrected claim resolves without a formal appeal. The exceptions are genuine plan exclusions and medical-necessity arguments, where you need documentation.
The three variants
1. Diagnosis not covered under the plan
Some diagnoses are excluded from coverage by the plan's benefit design, not because the ICD-10 code is wrong but because the plan does not cover that condition. Common examples: cosmetic diagnoses, certain infertility codes, weight-management diagnoses on plans without that benefit, and experimental or investigational indications. The RARC on the ERA will often point toward a coverage exclusion rather than a coding problem.
- Confirm the plan's exclusion list actually covers this diagnosis before accepting the denial. Payer coverage policies are not always applied consistently, and some exclusion denials arrive in error.
- If the underlying condition qualifies under a different, covered diagnosis, document the clinical basis and submit a corrected claim with the correct primary code. Do not change a code to something the documentation does not support.
- When the exclusion is accurate and the service was truly not covered, the patient may owe the balance depending on the plan's structure. Check whether the EOB reassigns the balance to patient responsibility before billing the patient.
2. Missing diagnosis code
This is the most straightforward CO-167 situation. The claim reached the payer without any diagnosis code in the required field, or with a blank or placeholder value that the adjudication system could not read.
- Check the original claim in your system to confirm whether the diagnosis was ever entered or simply failed to export to the 837 transaction.
- Submit a corrected claim (claim type 7 on the 837P, "corrected claim" in most portals) with the original claim number. Do not submit as new; that creates a duplicate denial.
- If the same pattern repeats across multiple claims, audit the charge entry or interface configuration for that procedure code or department. A blank diagnosis on every claim for a specific code is a setup problem, not individual coder error.
3. Invalid or expired ICD-10 code
ICD-10 codes are updated each October 1. Codes retire, change, or get replaced. A code that was valid on the date of service last year may not map correctly under the current code set, and payers' adjudication systems reject submissions using deleted codes.
- Verify the code against the ICD-10-CM version applicable for the date of service, not the current year. A claim for a date of service in September always uses the prior-year code set.
- Common triggers: codes retired in the most recent October update, codes that were split into more specific subcategories, or laterality codes that were added (requiring selection of a more specific variant).
- The fix is a corrected claim with the valid code for the applicable ICD-10 version. Document the code change in the claim notes so the audit trail is clear.
How to identify which variant fired
The RARC (Remittance Advice Remark Code) that comes with CO-167 is the fastest way to distinguish the three causes. Look for it in the service-line detail of the 835 ERA, not just the claim-level summary. Denial management workflows that read only claim totals miss service-line remark codes entirely, which is why CO-167 often lands in a generic "coding" bucket rather than getting worked correctly.
If no RARC is present or it is not specific enough, call the payer's provider relations line and ask which of the three triggers applies. That conversation takes five minutes and saves guessing.
CO-167 vs. CO-16
These two codes are easy to confuse. CO-16 is a broad "claim lacks information needed for adjudication" code that applies to missing or inconsistent data across many claim fields. CO-16 is the catch-all for missing data; CO-167 is specific to the diagnosis field. When both appear on the same claim, work them independently. CO-16 may point to a different field than the diagnosis.
Preventing CO-167 recurrence
- Run an ICD-10 validity check in your charge entry system or clearinghouse before claims transmit. Most clearinghouses can be configured to flag expired or incomplete codes as a pre-submission edit.
- Each October 1, audit your charge master and favorite diagnosis lists against the updated ICD-10-CM. Codes that changed are the source of a denial wave in November if left uncorrected.
- For procedures that commonly get CO-167 for non-covered diagnoses, build an advance notice into the scheduling workflow. Informing the patient before the service is far cleaner than billing disputes after the fact.
The bottom line
CO-167 almost always has an administrative fix. Check the RARC first, confirm which of the three triggers is active, then pick the right path: corrected claim for missing or invalid codes, a coverage or medical-necessity argument for non-covered diagnoses. See the revenue leakage guide for context on how coding denials compound into systematic revenue loss when they are not worked promptly.