CO 198 denial code

What CO-198 means

CO-198 means the payer found your authorization but the claim asked for more than it allows. You cleared the first hurdle (approval exists) and then billed past its limits: extra units, extra visits, a date outside the approved span, or a frequency above what was certified.

Because the group code is CO, the overage is a contractual obligation. The patient cannot be billed for services delivered beyond the authorization; the practice absorbs whatever the appeal process cannot recover.

Common causes

• Therapy or behavioral health visits continued after the authorized visit count ran out, and nobody requested more.
• The claim reports more units on a line than the authorization certified.
• Treatment ran past the authorization’s end date: approvals expire, and services after expiry count as unauthorized.
• The plan of care changed mid-treatment, adding sessions or services the original request never covered.
• Two departments or clinicians drew from the same authorization without a shared count, so the pool exhausted earlier than either realized.

How to fix and resubmit

1. Pull the authorization and compare it line by line with the claim: approved codes, units, visit count, and date range. Identify exactly what was exceeded and by how much.
2. If the claim is wrong (units keyed incorrectly, wrong date of service), submit a corrected claim. Some CO-198 denials are data-entry errors, not utilization problems.
3. If the services genuinely exceeded the authorization, ask the payer about extending or expanding it retroactively. Submit the request with progress notes showing why continued treatment was necessary. Once approved, resubmit or ask for reprocessing.
4. If the payer refuses a retro extension, appeal the denied portion with clinical documentation of medical necessity. An appeal that shows measurable progress and a clear treatment rationale is the only remaining route to payment.
5. If the appeal fails, write off the excess. Bill and collect normally for the portion inside the authorization; only the overage denies under 198.

How to prevent it

Track authorization consumption in real time. Your PM system should decrement remaining visits or units at check-in and alert staff two or three visits before exhaustion, leaving time to request more. Treat authorization end dates like expiry dates on the schedule: block bookings past the end date until an extension is confirmed. When a provider changes the plan of care, make an updated authorization part of the change workflow. Reauthorization requests submitted before the current approval runs out almost always beat retro requests submitted after a denial.

Compare with CO-197 (authorization absent) and CO-119 (the plan’s own benefit maximum reached, no authorization can override that one). Full series at the denial codes index.