What does denial code CO-198 mean?

CO-198 means an authorization was on file but the services billed exceeded what it approved - more visits or units than allowed, services after the end date, or codes the authorization did not cover.

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

CO-197 means no valid authorization existed at all. CO-198 means one existed and was exceeded. CO-198 is generally easier to resolve because the payer has already agreed the treatment was appropriate, so an extension request is a continuation rather than a fresh argument.

CO-198: The authorized limit for this service was exceeded

CO-198 is the denial that catches practices doing everything right at the start. The authorization was obtained, the service was necessary, and the course of treatment simply ran longer than the approval covered. Because part of the claim usually pays, it is easy to miss in posting. The fix is almost always administrative - an extension request - and it is far easier to obtain before the approved units run out than to argue for retroactively.

What it means: An authorization existed, but the services billed went beyond the visits, units, or date range it approved.
Who pays the balance: Contractual for the excess unless valid advance notice was obtained before exceeding the authorized amount.
Group code CO: Contractual Obligation - the provider absorbs the balance and cannot bill the patient

Why CO-198 happens

Treatment continued past the number of visits or units the authorization approved.
Services were delivered after the authorization's end date, even though the total units were not exhausted.
The authorization covered specific procedure codes and additional codes were billed alongside them.
A second provider in the same group drew on the same authorization without it being tracked centrally.
The approved units were consumed faster than planned because the treatment frequency increased.

How to fix a CO-198 denial

1
Pull the authorization and compare it line by line to what was billed
Check units, date range, and the specific codes approved. The mismatch is usually in one of the three and identifying which one determines the remedy.
2
Request an extension with evidence of continued need
Payers grant extensions when documentation shows measurable progress and a clear plan. Some will backdate to cover services already delivered, though this varies and should not be assumed.
3
Check whether only the excess denied
Frequently the authorized portion paid and only the overage denied, which changes both the amount at risk and how the balance should be handled.
4
Establish patient responsibility for continuing care
Once the authorization is exhausted and no extension is granted, further services need a signed advance notice before delivery for those balances to be collectible.

Deadlines depend on the payer

Filing limits and appeal windows for CO-198 vary by payer and often by plan type within the same payer. Look up the specific payer to see its verified deadlines and the source document they came from.

Browse payer billing references

Preventing CO-198 denials

Track authorized units and end dates in the scheduling system so the front desk sees the remaining balance when booking.
Request extensions before the last approved visit rather than after the denial, when the argument is much stronger.
Centralise authorization tracking across providers in the group so two clinicians do not silently draw on the same approval.

CO-198 frequently asked questions

What does denial code CO-198 mean?: CO-198 means an authorization was on file but the services billed exceeded what it approved - more visits or units than allowed, services after the end date, or codes the authorization did not cover.
What is the difference between CO-198 and CO-197?: CO-197 means no valid authorization existed at all. CO-198 means one existed and was exceeded. CO-198 is generally easier to resolve because the payer has already agreed the treatment was appropriate, so an extension request is a continuation rather than a fresh argument.

Related denial codes

CO-197 CO-39 CO-119 CO-151

Last reviewed August 5, 2026.

Denial code explanations are original plain-English summaries written for reference and are not the official X12 code descriptions. Payer handling of any code varies by contract - always verify against the remittance advice and your payer agreement before adjusting a claim.