What does CO-198 mean?

CO-198 is a Contractual Obligation (CO) denial: "Precertification/authorization/notification/pre-treatment exceeded." An authorization existed, but the service went beyond what it covered — more units, visits, or a longer span than the authorization approved — so the excess was denied.

CO · Contractual ObligationCARC 198

Denial Code CO-198

Q: Is CO-198 the patient's responsibility or a provider write-off?

CO-198 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 exceeded.

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

What CO-198 means

An authorization existed, but the service went beyond what it covered — more units, visits, or a longer span than the authorization approved — so the excess was denied.

Why CO-198 happens

Services delivered exceeded the authorized number of visits or units
Care continued past the authorization's approved date span
The procedure performed was broader than what was authorized
Additional medically necessary services were provided without extending the auth

What to do when you get CO-198

1Compare what was authorized (units, visits, dates, codes) against what was billed
2If the auth actually covered the services, correct the claim/auth reference and resubmit
3If the services genuinely exceeded the auth, request an extension/retro-authorization with clinical justification
4Document the medical necessity for the additional services to support an appeal or extension

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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-198?

If the authorization in fact covered the billed services and the claim just didn't reflect it, that's a corrected claim. If care legitimately exceeded the approved amount, appeal or request an authorization extension with the clinical records showing the additional services were medically necessary. Many plans allow a short retro window to extend an exceeded authorization.

Timing & deadlines

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

Example

A therapy plan is authorized for 12 visits but 16 medically necessary visits are delivered. Visits 13-16 return CO-198 (authorization exceeded). Requesting an authorization extension with the progress notes supporting continued necessity can recover the additional visits.

Prevent CO-198 going forward

Track authorized units/visits/dates against what's been delivered in real time
Request an extension BEFORE exceeding the authorized amount when more care is needed
Verify the auth covers the exact codes, units, and date span before each service
Flag authorizations nearing their limit so care doesn't outrun approval

Code families most affected

Therapy and rehabilitation services with visit/unit caps
Authorized procedure series and infusions
High-cost drugs/DME with quantity authorizations

Related codes

Denial codes you'll often see alongside CO-198

CO-197 CO-284 CO-151

Payer notes

CO-198 means the authorization was EXCEEDED (distinct from CO-197, authorization absent, and CO-284, authorization doesn't apply to the billed services). The fix hinges on whether an extension can be obtained for the additional, medically necessary care.

Turn this CO-198 denial into a sent appeal

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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.