CO-97, CO-4, and OA-23 Are Not Billing Problems. They're Credentialing Data Problems.

The Denial Code Is Not the Problem

A mid-size primary care group in the midwest starts seeing a cluster of CO-97 denials. The billing manager pulls the report, flags the claims, and routes them to the appeals queue. Standard procedure. A few weeks later, the same providers are throwing the same codes. The appeals resolved some of it, but the denials kept coming.

What nobody checked was whether the rendering provider's taxonomy code on file with the payer still matched what was on the claims. It didn't. It hadn't for about two months, ever since a payer did a quiet directory refresh. The credentialing record was stale. Every claim built on that record was going to misfire until someone fixed the upstream data.

That's not a billing story. That's a credentialing data story.

And from what we're seeing across the 820,757 provider records we monitor, it's one of the most common misdiagnoses in revenue cycle management.

What CO-97, CO-4, and OA-23 Are Actually Telling You

These three codes show up constantly in denial reports, and they get treated as billing execution failures. I think that framing is wrong most of the time.

CO-97 fires when the benefit for the service or procedure has been included in an allowance or payment for another service. In practice, a significant share of CO-97 denials trace back to a taxonomy or specialty mismatch between what the payer has on file for the provider and what the claim reflects. If a provider's credentialing record at the payer lists them under the wrong specialty, certain procedure codes will deny automatically because the payer's system doesn't recognize that provider as eligible to bill for that service.

CO-4 is a modifier-related denial, but the modifier problem is frequently downstream of a credentialing setup problem. When a provider's enrollment record doesn't correctly reflect their scope of practice or their supervising provider relationship, the claim either goes out with the wrong modifier or gets rejected when the modifier doesn't match the credentialing data the payer holds.

OA-23 covers contractual adjustment scenarios where the payer believes a different payer is primary. A lot of OA-23 denials are straightforward COB issues. But a subset of them, particularly in multi-location group practices, trace back to an NPI or group enrollment mismatch: the claim was submitted under a provider NPI linked to a location or group contract that the payer doesn't recognize as primary for that patient's plan.

None of these are problems you can permanently fix at the claims level. You can appeal your way through individual denials. You cannot appeal your way out of a credentialing data mismatch. The mismatch will keep generating denials until someone fixes the source record.

The Structural Problem: Credentialing Data Drifts Silently

This is the part that I think the industry underestimates. Credentialing data doesn't fail loudly. A provider revalidates with CMS. A payer updates their internal directory. A group practice adds a satellite location. A provider's DEA registration renews under a slightly different address. Each of these events can create a mismatch between what your credentialing system holds and what the payer actually has on file, and you won't know about it until claims start misfiring.

The scale of this is significant. According to an RCM analysis across 190 specialty practices by Medical Billers and Coders (2026), 61% of practices have at least one active credentialing lapse at any given time. Credential-related issues account for an estimated 42% of total claim denials, putting over $856,000 of annual revenue at risk for a 10-physician group, based on standard denial rate assumptions applied to average physician revenue (MD Clarity, updated June 2025).

The average coding-related denial dollar amount surged 126% in 2024, reaching $631 per claim, up from $297 in 2023, according to the American Hospital Association's Trailblazers report (February 2025). The rework cost compounds that: $118 per claim to remediate a credentialing-linked denial, and up to 35% of those denials are never reimbursed even after resubmission, according to Prime Credential (October 2025).

When you do the math on those numbers, the case for attacking this problem at the source rather than the symptom becomes obvious pretty quickly.

The Misdiagnosis Happening Across the Industry

We monitor 820,757 provider records across 206,422 practices. Right now, 12,019 of those practices have at least one active data mismatch flagged in our pipeline. That's roughly 1 in 17 practices carrying a known data discrepancy that could trigger a denial the next time a claim goes out under an affected provider.

What I keep thinking about when I look at that number is how many of those practices are currently working a denial queue that traces back to one of those mismatches, without knowing it. They're in the CO-97 appeals loop. They're resubmitting CO-4 claims. They're arguing OA-23 with the payer. And the credentialing record that caused all of it is sitting there unchanged.

The 70% preventability figure from Prime Credential and MedTrainer (2025, 2026) isn't shocking to me. Most of these denials have a data trail. The problem is that the trail runs through credentialing, not through billing, and most practices don't have tooling that connects those two layers.

What Argoseer Does Here, and What It Doesn't

Argoseer monitors provider records continuously against primary sources: NPPES, state license boards, DEA, OIG exclusion lists, and payer directory data where available. When a record changes at the source and that change creates a mismatch with what a practice's credentialing system holds, we flag it. The alert includes the specific field that changed, the source of the change, and the date it was detected.

The intent is to shorten the detection window. Instead of finding out about a taxonomy mismatch when a CO-97 denial lands, a practice manager can see the drift when it happens and route it to whoever handles credentialing updates before claims go out.

We're not a CVO. We don't perform primary source verification in the NCQA sense, we don't issue credentials, and we don't guarantee license validity. Your credentialing system tracks what you filed. We verify whether it's still true.

For practices that are watching denial codes and wondering why the same ones keep coming back, the answer is usually upstream. That's where we look.

If you want to see what we're detecting across your provider roster, our monitoring dashboard is a good starting point. Visit argoseer.com/product/monitor to see how it works.