CO 302 denial code

Claim adjustment reason code 302. Often reported as CO 302.

Authorization request window has passed

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 302 means

The deadline for getting precertification, notification, or authorization for this service passed before the request was made.

Payers set time frames for requesting approval, such as before the service or within a set period after an emergency admission. This code says the request came too late or never came within that window.

Some payers allow late requests with justification, but many do not. The group code and contract decide who carries the balance.

Group codes seen with 302

On a remittance, 302 comes after a group code. These are the ones it is most often reported with:

• CO 302 (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 authorization was requested after the service when the payer required it before.
• Notification of an urgent admission was made after the payer's deadline.
• The office did not know authorization was required until the claim denied.

What to do next

1. Check the payer's authorization timing rules for the service.
2. Appeal with proof of timely request or an explanation of why it was not possible, if the payer allows.
3. Add authorization timing checks to scheduling and admission workflows.

Related codes

• 197 (reason code) No prior authorization on file
• 284 (reason code) Authorization does not match services