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CO-286 Denial Code: Appeal Time Limit Not Met

CO-286 means the payer didn't consider your appeal because it was filed after the appeal time limit. The original denial stands. Unless you can prove the appeal was filed on time or the payer accepts a good-cause exception, the amount is usually written off.

Quick facts

Code
CO-286 (CARC 286)
Status
Active In use since November 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The provider absorbs the amount; the patient isn't billed because of a missed provider appeal deadline.
Official description
Appeal time limits not met
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-286 means

CARC 286 says appeal time limits were not met. The payer received your appeal after its deadline, so it didn’t review the merits. The original denial stands.

Every appeal level has a deadline, usually counted from the date of the denial notice or remittance. Medicare’s redetermination request, for example, generally must be filed within 120 days of receiving the initial determination, with separate deadlines for later levels. Commercial payers and Medicaid programs set their own limits in contracts and provider manuals, and those can be shorter.

This is different from CO-29, which applies when the original claim was filed late. With CO-286, the claim was filed and denied, and the dispute arrived too late.

Common causes

  • Denials not worked promptly, often because they weren’t visible in a work queue.
  • Deadline counted from the wrong date, such as the date the ERA was posted instead of the remittance date.
  • Appeal first sent incorrectly, then refiled after the deadline (CO-285).
  • Waiting for records from another provider or facility.
  • Mail delays without proof of the sending date.
  • Short payer-specific deadlines that staff didn’t know about.

How to fix it

  1. Check your records for proof the appeal was sent on time: certified mail receipts, fax confirmations, portal submission logs.
  2. If you have proof, send it to the payer and ask it to accept the appeal.
  3. Request a good-cause exception if the delay was due to circumstances the payer recognizes, with documentation.
  4. If neither applies, write off the amount as an administrative adjustment. Don’t bill the patient.
  5. Record the root cause for prevention.

How to prevent it

  • Track appeal deadlines by payer and level in your denial management system.
  • Work denials in order of deadline, not just dollar amount.
  • Use electronic submission where possible for time-stamped proof.
  • Request records early when an appeal will need outside documentation.
  • Monitor denial aging. An ERA Analyzer can surface denials approaching their appeal deadlines. See how to read CARC and RARC codes.

Remark codes that may appear with CO-286

  • N921 (The time limit for filing a reconsideration or appeal has expired.): The time limit for filing a reconsideration or appeal has expired.
  • N211 (Alert: You may not appeal this decision.): Alert that you may not appeal this decision.
  • CO-29 (The time limit for filing has expired.): The time limit for filing the original claim expired, a different deadline.
  • CO-285 (Appeal procedures not followed): Appeal procedures weren't followed.
  • CO-193 (Original payment decision is being maintained.): The original payment decision is maintained after review on the merits.
  • CO-B4 (Late filing penalty.): Late filing penalty on a claim that was paid.

CO-286 FAQ

How long do I have to appeal?

It depends on the payer and appeal level. Medicare sets specific timeframes for each level, such as 120 days from the initial determination to request a redetermination. Commercial and Medicaid deadlines vary by contract, plan, and state.

Can a late appeal still be accepted?

Some payers accept late appeals for good cause, such as a payer error, a natural disaster, or not receiving the denial notice. Medicare has a good-cause process. Explain the reason and include documentation.

What if the payer received the appeal on time?

Send proof, such as a certified mail receipt, fax confirmation, or portal submission record, and ask the payer to accept the appeal.

Can I bill the patient after CO-286?

No. The CO group code means the provider is responsible.

Does a reopening have a different deadline than an appeal?

Often yes. Medicare, for example, allows reopenings for certain clerical errors under separate time limits. Some commercial payers have similar correction processes. Check whether your issue qualifies.