What does CO-284 mean?

CO-284 is a Contractual Obligation (CO) denial: "Precertification/authorization/notification/pre-treatment number may be valid but does not apply to the billed services." An authorization number is on the claim and may be valid, but it doesn't match the services billed — the auth was for different codes, units, dates, or a different site than what was performed.

CO · Contractual ObligationCARC 284

Denial Code CO-284

Q: Is CO-284 the patient's responsibility or a provider write-off?

CO-284 carries the CO group code (Contractual Obligation): Provider/contractual responsibility — not billable to the patient while denied. A CO adjustment is the provider's responsibility, not the patient's: balance-billing the patient for a CO amount is a contract (and often compliance) violation. But CO does not automatically mean “write it off.” When the cause is fixable — missing information (CO-16), a modifier problem (CO-4), or NCCI bundling (CO-97) — you correct and resubmit, or appeal with documentation. You only truly write the amount off when it is a final contractual adjustment, such as the fee-schedule difference on CO-45.

Precertification/authorization/notification/pre-treatment number may be valid but does not apply to the billed services.

Source: X12 Claim Adjustment Reason Codes (CARC) & Group Codes. Maintained by the D3rx Clinical Billing Team.

What CO-284 means

An authorization number is on the claim and may be valid, but it doesn't match the services billed — the auth was for different codes, units, dates, or a different site than what was performed.

Why CO-284 happens

The authorization covered a different procedure code than the one billed
The service was performed at a site or date the authorization doesn't cover
The units or scope billed don't match what was authorized
The wrong authorization number was attached to the claim

What to do when you get CO-284

1Compare the authorization (codes, units, dates, site) against exactly what was billed
2If the right auth exists but the wrong number was used, correct the reference and resubmit
3If the service differs from what was authorized, request an authorization that matches the actual service
4Document medical necessity to support a corrected or new authorization

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CO group code: who absorbs the charge

Contractual Obligation — Provider/contractual responsibility — not billable to the patient while denied.

A CO adjustment is the provider's responsibility, not the patient's: balance-billing the patient for a CO amount is a contract (and often compliance) violation. But CO does not automatically mean “write it off.” When the cause is fixable — missing information (CO-16), a modifier problem (CO-4), or NCCI bundling (CO-97) — you correct and resubmit, or appeal with documentation. You only truly write the amount off when it is a final contractual adjustment, such as the fee-schedule difference on CO-45.

Appeal, correct, or write off CO-284?

CO-284 is about a mismatch, not an absent auth, so first reconcile the auth to the service. If a valid authorization for the billed service exists and the claim cited the wrong one, correct the reference and resubmit. If the service genuinely fell outside the authorization, request a matching/retroactive authorization with clinical justification, then resubmit or appeal with that authorization attached.

Timing & deadlines

Act promptly — corrected-authorization and appeal windows are short. Standard anchors apply (Medicare redetermination 120 days from the remittance; commercial ~180 days), and retro-auth requests often cap at a few business days after the service or denial.

Example

An MRI is authorized for the lumbar spine, but the study performed and billed is cervical. The payer returns CO-284 because the valid auth doesn't apply to the billed service. Obtaining an authorization for the cervical study and resubmitting resolves it.

Prevent CO-284 going forward

Verify the authorization matches the exact code, units, site, and date before the service
Attach the correct authorization number to the claim
Re-check the auth if the planned service changes before it's performed
Maintain a payer-by-service authorization grid and keep it current

Code families most affected

Advanced imaging (CT/MRI/PET) with site-specific authorizations
Authorized procedures where the performed service may differ
High-cost drugs/DME with code-specific authorizations

Related codes

Denial codes you'll often see alongside CO-284

CO-197 CO-198

Payer notes

CO-284 means the authorization exists but DOESN'T APPLY to the billed services — distinct from CO-197 (authorization absent) and CO-198 (authorization exceeded). Reconcile the auth to the actual service before appealing.

Turn this CO-284 denial into a sent appeal

D3rx drafts a ready-to-send, e-signable appeal letter for CO-284 from your claim details — free, backed by CMS, Medicare, and major-payer data.

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Medical billing disclaimer

CARC/RARC definitions are the standardized X12 set; group-code semantics follow the X12 Claim Adjustment Group Code standard. Filing and appeal windows vary by payer — the standard anchors shown (Medicare redetermination 120 days from the remittance; Medicare timely filing 12 months from date of service; most commercial payers ~90-180 days) are general references, not a guarantee for any specific plan. Always confirm the rule in the payer's provider manual before acting. D3rx is not responsible for claim outcomes.