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CO-284 Denial Code: Authorization Doesn't Match Services

CO-284 means the authorization number on the claim may be valid, but it doesn't apply to the billed services. The approved codes, dates, units, or setting don't match what was billed, so the payer treats the service as unauthorized.

Code: CO-284 (CARC 284)
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 unless the claim or authorization is corrected; the patient isn't billed.
Official description: Precertification/authorization/notification/pre-treatment number may be valid but does not apply to the billed services.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-284 means

CARC 284 says the precertification, authorization, notification, or pre-treatment number may be valid but does not apply to the billed services. The payer found the authorization you reported in box 23 (or the 837’s prior authorization reference), but the services on the claim aren’t the ones it approved.

The distinction matters. With CO-197, nothing was authorized. With CO-284, the authorization process happened, but something about the billed services doesn’t match: the code, the dates, the units, the setting, or the service line. That usually makes CO-284 easier to resolve, especially when the difference is a coding choice or a clinically justified change.

For a broader look at authorization problems, see authorization and referral denials.

Common causes

Different procedure performed than the one approved, for example when the surgical plan changed during the procedure.
Code billed differs from the code on the authorization, even for the same service.
Dates outside the approved window, such as a rescheduled service.
Place of service or facility changed, for example from a hospital outpatient department to an ambulatory surgery center.
Authorization for one service used for another on a multi-line claim.
Units or visits beyond what the authorization covers (sometimes reported as CO-198).

How to fix it

Compare the authorization to the claim line by line: codes, dates, units, place of service, and facility.
If the claim was coded wrong, correct it to match the documented service and send a corrected claim with resubmission code 7 in box 22.
If the service legitimately changed, contact the payer to update or retro-authorize, then request reprocessing.
If the authorization was for a different provider or location, see whether the payer can transfer it (CO-296 covers provider mismatches).
Appeal with the operative or clinical notes if the payer won’t update the authorization.

How to prevent it

Authorize the codes you expect to bill, including likely alternatives when the payer allows it.
Recheck authorizations when appointments are rescheduled or moved to another location.
Notify the payer promptly when a procedure changes during surgery.
Match authorization details before submission. A Claims Validator can compare billed codes and dates to the authorization on file.

Specialty notes

Surgical practices, imaging centers, and therapy practices see CO-284 most. Imaging authorizations are often code-specific, so adding or removing contrast can create a mismatch.

Remark codes that may appear with CO-284

N54 (Claim information is inconsistent with pre-certified/authorized services.): The claim information is inconsistent with the pre-certified or authorized services.
M62 (Missing/incomplete/invalid treatment authorization code.): The treatment authorization code is missing, incomplete, or invalid.

CO-197 (Precertification/authorization/notification/pre-treatment absent.): No authorization at all, rather than one that doesn't match.
CO-198 (Precertification/notification/authorization/pre-treatment exceeded.): Authorization exceeded, when services go beyond approved units or visits.
CO-296 (Precertification/authorization/notification/pre-treatment number may be valid but does not apply to the provider.): The authorization may be valid but doesn't apply to the provider billing.
CO-302 (Precertification/notification/authorization/pre-treatment time limit has expired.): The authorization's time limit has expired.
CO-39 (Services denied at the time authorization/pre-certification was requested.): The authorization was requested and denied.

Authorization and Referral Denials: Prevention First: Authorization and referral denials are difficult to fix after care is delivered. Learn how practices can validate dates, services, units, and providers first.
CARC and RARC Codes: Read Denials From the ERA: Learn how CARC and RARC codes explain payer adjustments and denials, and how practices can turn ERA history into repeatable denial-prevention rules.
Medical Claim Denials: 10 Preventable Causes: Medical claim denials often start with preventable errors. Learn 10 denial causes practices can detect earlier with stronger claim validation.

CO-284 FAQ

How is CO-284 different from CO-197?

CO-197 means no authorization was found. CO-284 means an authorization exists and may be valid, but it covers different services than the ones billed.

What mismatches cause CO-284?

A different procedure code performed than the one approved, services outside the approved date range, a different place of service or facility, or an authorization for one service line applied to another.

Can the authorization be updated after the service?

Some payers allow retroactive updates when the approved service changes, for example when a surgeon performs a related but different procedure. Contact the payer's utilization management department quickly, since windows are often short.

Should I appeal or correct the claim?

If the claim was coded wrong, correct it. If the service changed for valid clinical reasons, request an authorization update and then reprocessing or appeal.

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