CO 286 denial code

Claim adjustment reason code 286. Often reported as CO 286.

Appeal filed too late

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 286 means

The appeal was not considered because it was filed after the payer's time limit for appeals.

Every payer sets a window for appeals that starts from the date of the denial or remittance. This code says your appeal arrived after that window closed, so the original decision stands.

Unless you can prove the appeal was filed on time, options are limited. Proof of timely submission is the main way to challenge it.

Group codes seen with 286

On a remittance, 286 comes after a group code. These are the ones it is most often reported with:

• CO 286 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• The appeal was filed after the payer's deadline.
• The appeal was first sent to the wrong place and the correct filing came too late.
• The payer did not receive or record an appeal that was sent on time.

What to do next

1. Check your records for proof that the appeal was sent on time, such as fax confirmations or portal receipts.
2. If you have proof, ask the payer to reopen the appeal with that evidence.
3. Review your denial workflow so appeals are tracked against each payer's deadline.

Related codes

• 285 (reason code) Appeal procedures not followed
• 29 (reason code) Timely filing limit has passed