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Claim adjustment reason code

CO-198: Prior authorization exceeded

CO-198 means: Precertification/notification/authorization/pre-treatment exceeded. An authorization exists. The problem is that you went past what it allowed — more units, more visits, or a longer date range than was approved.

Read the group code before you act on this

198 is the claim adjustment reason code. The CO in front of it is the group code — a separate field the payer sets on the remittance. The same reason code arrives under different group codes depending on the payer and the situation, and the group code, not the reason code, decides who owes the money.

CO — contractual obligation. You write it off. You may not bill the patient.
PR — patient responsibility. Billable to the patient.
OA — other adjustment, and PI — payer initiated reduction. Neither is patient responsibility.

What causes it

The approved unit or visit count was used up and treatment continued
Services were rendered after the authorization date range ended
The authorization covered a lower level of service than the one performed
A second course of treatment was billed against the first authorization
Nobody was tracking the remaining balance on the authorization while the patient was still in treatment

How to work it

Pull the authorization and count exactly what was approved against exactly what was billed — units, visits and date range, separately
Bill the portion that falls inside the authorization and handle the excess separately, rather than appealing the whole claim
For the excess, request an extension or retro-authorization with the clinical notes that justify why treatment continued
Where the payer allows it, ask for the extension BEFORE the last approved visit rather than after — several will not backdate at all

How to stop it recurring

This is a tracking failure, not a knowledge failure. Somebody has to hold the remaining balance on every open authorization and flag it before the last visit, which is exactly the job a prior authorization seat does.

Who does this work

A prior authorization seat at $1,900 per seat per month works this queue full time, during your business hours, inside your own system. Every call is logged with the payer reference number and the outcome, and every Friday you get it in writing.

What that seat does →

Codes worked the same way

CO-198 is answered with the document the payer names. So are these, which is why a queue sorted by recovery route moves faster than one sorted by code number — the same person, in the same system, with the same evidence to hand, clears all of them in one pass.

CO-252 — Additional documentation required
CO-226 — Requested information not supplied
CO-227 — Patient did not supply information
CO-251 — Documentation incomplete
N29 — Documentation missing

Specialties that name this among their costliest

These are specialties whose own worst denials include one of this kind. The line under each is the denial they name, quoted from their page so you can see what the link is based on.

Anesthesia
Time units miscalculated from an incomplete anesthesia record
Ophthalmology
Intravitreal injection paid for the administration but not the drug, because the units given and the amount discarded were never written into the note.
Otolaryngology
Endoscopic sinus surgery denied because the chart never pulls the failed medical management together — the drug trials, their dates and imaging findings sit in separate notes or nowhere.
Neurology
Nerve conduction study with needle EMG denied because the report gives only a summary impression instead of each nerve and muscle tested with its findings
Obstetrics & Gynecology
Global maternity package billed in full after the patient transferred care mid-pregnancy, when only the antepartum visits actually rendered here should have been itemised.
Urgent Care
Laceration repair paid at the simplest level because the note says the wound was closed but never records its length, its site or whether the closure was layered

What leaving it costs

Working a denied claim costs $57.23 per denied claim in administrative time. Source. At 100 denials a month — an illustration, not a measurement of your practice — that is $5,723 a month, or $68,676 a year, in labour alone.

The figure that makes it worth spending: about 90% of initially denied claims are eventually paid. Source. The reason a denial sits is almost never that nobody knows how to work it — it is that nobody has the hours.

Questions

What does denial code CO-198 mean?

Precertification/notification/authorization/pre-treatment exceeded. In plain terms: An authorization exists. The problem is that you went past what it allowed — more units, more visits, or a longer date range than was approved.

What causes CO-198?

The approved unit or visit count was used up and treatment continued. Services were rendered after the authorization date range ended. The authorization covered a lower level of service than the one performed. A second course of treatment was billed against the first authorization. Nobody was tracking the remaining balance on the authorization while the patient was still in treatment.

How do you fix a CO-198 denial?

Pull the authorization and count exactly what was approved against exactly what was billed — units, visits and date range, separately. Bill the portion that falls inside the authorization and handle the excess separately, rather than appealing the whole claim. For the excess, request an extension or retro-authorization with the clinical notes that justify why treatment continued. Where the payer allows it, ask for the extension BEFORE the last approved visit rather than after — several will not backdate at all.

Can CO-198 be prevented?

Is CO-198 the same as PR-198?

Same reason, different group code. The number 198 is the reason: An authorization exists. The problem is that you went past what it allowed — more units, more visits, or a longer date range than was approved. The prefix says who carries the amount. CO means contractual obligation — the payer says the amount is not billable to anybody, and it is written off unless the denial itself is overturned. PR-198 is the same reason assigned to patient responsibility — the payer says the amount is owed by the patient, and it is billed to them. Read the prefix before the number: it decides whether you appeal, write off, or bill the patient.

What is the difference between CO-198 and CO-197?

CO-198: An authorization exists. The problem is that you went past what it allowed — more units, more visits, or a longer date range than was approved. CO-197: The payer required prior authorization for this service and cannot find one attached to the claim. They are different reasons that happen to sit next to each other in the list, and they are worked differently — CO-198 is answered with the document the payer names; CO-197 is taken back to the authorization.

Code descriptions are the standard X12 claim adjustment reason and remittance advice remark code text. Payer policies differ, and the payer’s own coverage policy governs any individual claim. This page is working guidance, not legal or clinical advice.

Last updated 2026-09-12. This is operational guidance drawn from payer remittance practice, not legal, coding or reimbursement advice. Payer-specific rules vary and change; confirm against the payer’s own policy before acting on a specific claim.

Written by Ibtesam Asif · Last reviewed 2026-09-12

Code descriptions are the standard published text. Everything after them is operational guidance from our own work, and payer policy governs any individual claim.

Other denial codes

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