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CO-285 Denial Code: Appeal Procedures Not Followed

CO-285 means your appeal wasn't accepted because the payer's appeal procedures weren't followed, for example the wrong form, level, address, or missing required elements. The payer hasn't ruled on the merits; fix the process and resubmit if time remains.

Quick facts

Code
CO-285 (CARC 285)
Status
Active In use since November 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The original denial stands and the provider remains responsible unless a properly filed appeal succeeds.
Official description
Appeal procedures not followed
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-285 means

CARC 285 says appeal procedures were not followed. You tried to dispute a claim decision, but the payer didn’t accept the appeal because it wasn’t filed the way its process requires. The payer hasn’t decided whether you’re right about the original denial; it’s saying the request wasn’t valid as submitted.

Payers set their own appeal rules for commercial plans, and Medicare, Medicaid, and Medicare Advantage have defined appeal levels. Requirements often include specific forms, a first-level reconsideration before a formal appeal, a designated mailing address or portal, the original claim number, and a signed request with supporting documentation.

Common causes

  • Corrected claim sent instead of an appeal, or an appeal sent when the payer wanted a corrected claim or reopening.
  • Skipped level, such as filing a second-level appeal without completing the first.
  • Wrong form or channel, like mailing an appeal the payer requires through its portal.
  • Missing elements: claim number, member ID, dates of service, reason for appeal, or signature.
  • Appeal filed by the wrong party, for example a non-participating provider without the member’s authorization where one is required.
  • Appeal sent to the wrong payer or department, such as a delegated vendor handling the plan.

How to fix it

  1. Read the payer’s appeal instructions in the denial letter and provider manual.
  2. Identify what was wrong with the original submission.
  3. Refile correctly, using the required form, level, and channel, and include all required information and documentation.
  4. Check the deadline before refiling. If it has passed, see CO-286.
  5. Keep proof of submission for the refiled appeal.

How to prevent it

  • Keep an appeals guide by payer with forms, levels, addresses, portals, and deadlines.
  • Decide corrected claim versus appeal carefully. Coding or data errors usually need a corrected claim; disagreements about coverage or medical necessity usually need an appeal. See claim rejection vs. denial.
  • Use appeal templates that include all required elements.
  • Track appeals from submission to decision so rejected appeals are caught early.

Remark codes that may appear with CO-285

  • N368 (You must appeal the determination of the previously adjudicated claim.): You must appeal the determination of the previously adjudicated claim, rather than submitting a new claim.
  • N1 (Alert: You may appeal this decision in writing within the required time limits following receipt of this notice by following the instructions…): Alert that you may appeal in writing within the required time limits, following the instructions included.
  • CO-286 (Appeal time limits not met): Appeal time limits not met, a deadline issue rather than a procedure issue.
  • CO-193 (Original payment decision is being maintained.): The original payment decision is maintained after review.
  • OA-18 (Exact duplicate claim/service (Use only with Group Code OA except where state workers' compensation regulations requires CO)): Duplicate claim, which can result when an appeal is sent as a new claim.
  • CO-29 (The time limit for filing has expired.): Timely filing expired on the original claim.

CO-285 FAQ

What are common appeal procedure mistakes?

Sending a corrected claim when the payer wanted an appeal (or the reverse), using the wrong appeal form, skipping a required first level such as reconsideration, sending to the wrong address or portal, or leaving out required items like the original claim number or a signed request.

Does CO-285 mean I lost the appeal?

No. The payer didn't review the merits. You can usually refile correctly as long as the appeal deadline hasn't passed.

How do I find the payer's appeal procedures?

They're in the provider manual, the payer's website, and often on the denial notice itself. Medicare's appeal levels and forms are defined by CMS and the Medicare contractor.

Does the appeal deadline keep running?

Usually yes. An improperly filed appeal may not stop the clock, so refile quickly.

Can I bill the patient after CO-285?

No. The original denial's group code still applies, and a procedural problem with the provider's appeal doesn't shift responsibility to the patient.