CO 256 denial code

What CO-256 means

CO-256 tells you the managed care plan reviewed the claim and decided the service is not payable under the contract between your organization and the plan. This is not about the patient’s eligibility or the medical necessity of the care; it is about what your participation agreement says the plan will pay for.

Because the group code is CO (contractual obligation), the amount is a provider write-off. You cannot bill the patient. That distinguishes it from PR-204, where the benefit plan excludes the service and the patient is responsible.

You will see CO-256 mostly from Medicaid managed care organizations and Medicare Advantage plans, and the specifics vary widely by plan. Always read the accompanying remark codes: plans often use CO-256 as a catch-all with the real reason in the RARC.

Common causes

1. The service is carved out of your contract, for example behavioral health or lab work routed to a different contracted vendor.
2. The rendering provider or service location is not credentialed under the contract for that service line.
3. A required authorization or referral pathway defined in the contract was not followed (some plans use CO-197 for this instead; others lump it into 256).
4. The service is bundled or capitated: payment already flows through a per-member-per-month arrangement, so fee-for-service claims deny.
5. The plan considers the code experimental, cosmetic, or otherwise excluded under the contract’s covered-services list.
6. Plan-specific edits: some state Medicaid MCOs use CO-256 for taxonomy, roster, or enrollment mismatches. The remark code is the only way to tell.

How to fix and resubmit

1. Pull the remittance and note every remark code paired with CO-256. Work from the remark code, not the CARC alone.
2. Check the payer portal or call provider services and ask the concrete question: which contract provision made this non-payable?
3. If it is a credentialing or roster gap, fix the roster with the plan, then ask whether claims during the gap can be reprocessed. Some contracts allow it; many do not.
4. If the service is capitated or carved out, do not resubmit. Route future orders to the contracted vendor and write off the claim.
5. If the contract does cover the service, appeal within the plan’s window (commonly 60-180 days; check the provider manual). Attach the relevant contract page or fee schedule line. Vague appeals lose.
6. Do not shift the balance to the patient while the appeal is pending. It stays CO unless the plan reprocesses it under a PR group code.

How to prevent it

• Keep a current summary of each managed care contract: covered service lines, carve-outs, capitated services, and credentialing requirements. Front-end staff cannot honor a contract nobody has summarized.
• Verify the rendering provider is on the plan’s roster before scheduling new service lines under a contract.
• Confirm authorization and referral rules per plan, not per payer brand; the same insurer’s HMO and PPO products often differ.
• When contracts renew, have someone compare the new covered-services exhibit against your charge master and flag anything that moved.
• Trend CO-256 by plan monthly. A cluster from one plan usually means one contract change, and catching it early limits the write-offs.