Denied after prior authorization was approved: why it happens and what to do
You got the authorization. The approval is in the chart. The service was performed.
Then the claim denies anyway.
That does not necessarily mean the authorization was useless. In many cases, something on the claim does not match the approval the payer has on file.
The fastest way to work the denial is to compare the authorization and the claim side by side.
The most common reasons an authorized claim still denies
The billed code does not match the authorized code
The procedure may have changed, an additional service may have been performed, or the authorization may have been requested under a different code.
Even a valid authorization may not apply if the claim is submitted for a different service.
The date of service falls outside the authorization window
A procedure gets rescheduled, but the authorization dates do not get updated.
The service may still have been appropriate, but the payer's system sees a date outside the approved period.
The claim has more units than were authorized
This comes up with services such as drugs, therapy, imaging, and other treatments where the authorization includes a specific quantity.
If the claim exceeds that amount, the payer may deny all or part of it.
The provider or location does not match
An authorization may be tied to a specific rendering provider, facility, or location.
If the claim shows a different provider or site, the payer may treat it as an unauthorized service.
The authorization number is missing or incorrect
Sometimes the authorization itself is fine.
The claim simply does not contain the correct number, or the number is entered in a way that does not match what the payer expects.
The patient's coverage changed
Eligibility can change between the date the authorization is obtained and the date the service is performed.
That is why an authorization should not replace an eligibility check close to the date of service.
Medical necessity is reviewed again
An authorization is not always a guarantee of payment.
Depending on the payer and plan, the claim may still be subject to eligibility, benefit, documentation, coding, or medical-necessity requirements.
Denial codes you may see
A few adjustment codes commonly associated with these situations include:
- CO-15: The authorization number may be missing, invalid, or not applicable to the billed service or provider.
- CO-197: Precertification or authorization was absent.
- CO-50: The service was not considered medically necessary.
The adjustment code is a starting point, not the full answer.
The denial notice, remittance details, authorization record, and payer policy should be reviewed together before deciding whether the next step is a corrected claim, reconsideration, appeal, or another type of follow-up.
What to do next
1. Compare the claim and authorization line by line
Check:
- CPT or HCPCS code
- Units
- Date of service
- Rendering provider
- Facility or location
- Authorization number
- Effective dates
A small mismatch may explain the entire denial.
2. Correct the claim if the claim was wrong
If the authorization was valid but the claim contained incorrect information, determine whether a corrected claim is appropriate under the payer's rules.
Fixing the underlying mismatch is usually more useful than appealing a claim that was submitted incorrectly.
3. Appeal when the claim matches the approval
If the billed service matches the authorization, gather the documentation that supports the case.
That may include:
- Authorization or approval letter
- Authorization number
- Portal confirmation
- Relevant clinical documentation
- Prior payer correspondence
The appeal should make it easy for the payer to see that the service billed is the service that was approved.
4. Review options when the procedure changed
Sometimes the service changes for a legitimate clinical reason after the authorization was obtained.
Check whether the payer allows an authorization update, retrospective authorization, or another correction process.
The sooner that is addressed, the better.
5. Document payer follow-up
Keep call reference numbers, portal confirmations, correspondence, and notes from payer conversations.
If the claim requires escalation later, that history matters.
How to prevent the same denial next time
The best authorization workflow does not end when the approval is received.
Before the service and before the claim goes out, confirm that:
- Eligibility is still active.
- The authorization has not expired.
- The approved code still matches the service performed.
- Units are within the approved amount.
- The rendering provider and site match.
- The authorization number is included correctly.
If the procedure changes, route the case for authorization review before billing whenever possible.
The goal is not just to overturn one denial. It is to stop the same mismatch from happening again.
Seeing more of these denials than you should?
Vero's Free Revenue Leak Audit reviews your existing denials and claim data, including claims that had prior authorization, and identifies issues that may still deserve follow-up.
You do not have to switch billing companies first.
Common questions about denials after prior authorization
Doesn't an approved prior authorization guarantee payment?
No. An authorization generally applies to a specific service and set of conditions. Payment may still depend on eligibility, coding, documentation, benefits, and the terms of the patient's plan on the date of service.
How long do I have to appeal?
Appeal deadlines vary by payer and plan. Check the denial notice and applicable payer requirements rather than assuming the same deadline applies to every claim.
Can an authorization be updated after the procedure?
Some payers may allow an authorization update or retrospective review in certain circumstances. The available options depend on the payer and the reason the service changed, so the practice should address it as soon as possible.