CO-167
Sometimes appealableThis diagnosis is not covered
Group CO — Contractual Obligation — an adjustment tied to the contract between the insurer and the provider. You usually cannot be billed for a CO amount.
CO-167 means the plan doesn't cover the diagnosis (or diagnoses) associated with the claim. Some plans exclude coverage for particular conditions or for services tied to certain diagnoses.
It's a Contractual Obligation (CO). Sometimes the real issue is that a covered diagnosis wasn't coded, or an additional diagnosis would justify coverage — both of which can be addressed.
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Why you're seeing CO-167
- The plan genuinely excludes the billed diagnosis.
- A covered secondary diagnosis wasn't coded on the claim.
- The wrong diagnosis code was entered.
Can you appeal it?
Depends on whether the exclusion is real — appeal or resubmit when a covered diagnosis applies or was miscoded.
What to do next
- 1Ask which diagnosis and plan exclusion the denial is based on.
- 2Check whether a covered or additional diagnosis should have been coded.
- 3If the coding was wrong, have the provider resubmit with the correct diagnosis.
- 4Appeal with clinical support if the diagnosis should be covered under your plan.
Evidence that helps
- Chart notes supporting the correct or additional diagnosis.
- The plan provision listing the diagnosis exclusion.
Frequently asked questions
Can a diagnosis really be excluded?
Some plans do exclude coverage for services tied to specific diagnoses. But first check whether the right diagnosis was coded — a missing or incorrect diagnosis code is a common and fixable cause of CO-167.
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Other common denial codes
Last reviewed July 18, 2026. Denial-code lists (CARC/RARC) are updated three times a year; we review these explanations against the current list.
Sources & references
These explanations are written in plain language and based on the authoritative sources below. Always confirm the specifics against your own plan documents and denial letter.
- ASC X12 — Claim Adjustment Reason Codes (CARC)
The standards body that maintains the official CARC list (the CO/PR codes), updated three times a year.
- CMS / X12 — Remittance Advice Remark Codes (RARC)
The remark codes (N-/M- codes) that accompany a CARC and give the specific reason for an adjustment.
- HealthCare.gov — Appealing a health plan decision
Official overview of internal appeals and external review rights for Marketplace and most private plans.
- U.S. Department of Labor — ERISA claims & appeals
Governs claim and appeal procedures and deadlines for most employer-sponsored (ERISA) health plans.
- Your state's insurance regulator
State agencies enforce external review and consumer protections; find yours via the NAIC directory.
Important: this is not legal or medical advice.
AppealBrain is a free, self-help tool that helps you draft an appeal letter using the information you provide. We are not a law firm, medical provider, or insurance company, and using this tool does not create an attorney–client relationship. Appeal rules and deadlines vary by plan and state — always review your own denial letter and plan documents, and consider consulting a licensed professional for your specific situation. We do not guarantee any outcome.