CO-198 denial code
Precertification, authorization or notification exceeded
How to fix it
Request an authorization extension with documentation supporting continued medical necessity, and appeal the delivered visits.
How to prevent it
Track remaining authorized units per patient and request extensions before exhaustion rather than after.
In practice
A physical therapy practice obtains authorisation for twelve visits. The patient is progressing but needs more, and visits thirteen through eighteen are delivered while an extension request is pending. Those six visits return CO-198.
The authorisation was real and the care was appropriate. What failed is that the services were delivered before the extension was approved, and an authorisation covers a specific number of units — exceeding it denies exactly like having none.
The extension request should have gone in around visit nine, not after visit twelve. Requesting at the threshold rather than past it is the difference between an approved extension and six unpaid visits with a weak retroactive appeal.
What sits behind it
CO-198 is a tracking failure rather than an authorisation failure, and that changes where the fix belongs. Practices that treat authorisation as a one-time event at the start of care will hit this every time a course of treatment runs longer than expected — which is most of the time, in the service lines where it matters.
The services that generate this volume all share a shape: care delivered in a course rather than a visit. Physical and occupational therapy, behavioural health, chiropractic, infusion and home health all have authorisations denominated in units that deplete as care proceeds, invisibly, unless someone is counting.
Retroactive approval is possible with some payers where continued medical necessity is documented, but it is discretionary and the success rate falls the further past the limit the request arrives. The reliable version is a remaining-units field that is visible at scheduling, so the front desk sees the limit approaching before the clinician does.
Related codes
Terms used here — Prior Authorization · Medical Necessity · Appeal
How we handle it — Prior Authorization · Denial Management · Practice Analytics
Primary sources
The rules behind CO-198, at the bodies that publish them.
- CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) (opens in a new tab)
Centers for Medicare & Medicaid Services — The rule imposing prior authorization decision timelines and API requirements on impacted payers. It is the single largest scheduled change to authorization workflow this decade.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- Medicare claims appeals process (opens in a new tab)
Centers for Medicare & Medicaid Services — The five levels of appeal, what each requires and the deadline for each. Missing a level's deadline ends the appeal regardless of the claim's merits.
Every denial code with a guide
Authorization
Bundling
Contractual
Coverage
Data quality
Documentation
Eligibility
Liability and workers comp
Patient responsibility
Provider eligibility
Timely filing
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-198
CO-197 means authorisation was absent — none was obtained. CO-198 means authorisation existed but the services delivered went beyond what it approved, in number, duration or scope. CO-197 is a front-end failure; CO-198 is a tracking failure during a course of care.
Sometimes, through a retroactive extension supported by documentation of continued medical necessity. It is discretionary, and approval becomes less likely the further beyond the limit the request arrives, which is why extensions should be requested at the threshold rather than after it.
Anything delivered as a course rather than a single visit — physical and occupational therapy, behavioural health, chiropractic, infusion and home health. Their authorisations are denominated in units that deplete as care proceeds.
Track remaining authorised units per patient and make that count visible at scheduling, not just in the billing system. Request extensions when the remaining balance is low enough to be a problem, typically with two or three visits still available.
Find out what your denials are costing you
A free billing audit reviews your denial rate, AR aging and clean claim rate against industry benchmarks. Takes about two minutes to request. No sales pitch.
No setup fees · You pay when we collect · Pricing from 3% of net collections