Notes on payer behavior
Medical billing denials, by type: which ones a practice can get back
Medical billing denials come in six kinds, and they aren't equally worth your time. Three of them reverse with a corrected claim or a document and almost never need a physician. Two need a clinical argument. One is usually final. Sorting a year's denials into those piles, before anyone touches an appeal, is the single highest-return hour in a billing office. Here's the sort.
How common denials are
Around one claim in ten on first submission, and rising. Experian Health's 2025 State of Claims survey put the initial denial rate at 11.8 percent in 2024, up from 10.2 percent, with 41 percent of providers now above 10 percent (Experian Health). Premier's 2024 survey found nearly 15 percent of claims to private payers denied initially, and more than 60 percent of the denials providers fought were overturned, at about $44 of administrative cost per claim (Premier). The top causes named by respondents were missing or inaccurate claim data and authorization. Those aren't clinical disputes. They're paperwork.
The six types
| Type | Typical codes | What it usually is | Recoverable? |
|---|---|---|---|
| Registration and eligibility | CO-16, CO-22, CO-27, CO-31, CO-109 | Wrong or missing patient data, coverage that ended, wrong payer, coordination of benefits | Yes. Correct the claim or redirect it. The risk is the clock at the right payer. |
| Authorization | CO-197, CO-15 | No authorization matched to the claim, or the auth doesn't match the codes, dates, or units | Usually, when the auth exists. Retro-authorization is the only route when it doesn't. |
| Coding and bundling | CO-4, CO-97, CO-236, CO-150, CO-151, OA-18 | Modifier mismatch, NCCI edits, global periods, downcoding, false duplicates | Yes when the service was distinct or the level is documented. Some pairs can't be unbundled. |
| Timely filing | CO-29 | Late per the payer's records | With proof of timely submission or a COB exception. A genuinely late claim is gone. |
| Medical necessity | CO-50 | A coverage-policy mismatch, or a real clinical dispute | Mismatches yes. Clinical disputes are the physician's appeal, not a billing task. |
| Non-covered and benefit limits | CO-96, CO-204, CO-119 | Plan exclusions, frequency caps | Rarely, except miscounted limits and group-code corrections so the patient can be billed. |
Each code links to its own note in the denial codes table.
Where independent practices actually lose the money
Not on the dramatic denials. On the routine ones nobody works. A $180 injection denied CO-197 when the authorization was on file. A 99214 paid as 99213 by an algorithm. A bilateral procedure collapsed into a duplicate. Each is small, each is fixable, and each costs more in staff time to fix alone than it pays. So they sit in a queue, then age past the payer's window. Multiply by a year of volume and you have the number we keep finding: at an orthopedic practice in Miami, 30 percent of net insurance revenue had been paid short or denied for reasons that could have been fixed. Why none of it shows up on a report.
The triage order
- Count by code, by payer, by month. A year of remittances, one table. Patterns are visible instantly. How to pull it from the 835.
- Sort into the six types. Registration, authorization, and coding denials go first. They reverse on paper.
- Order by deadline, not by date of service. The oldest recoverable denial at the payer with the shortest window goes first. The Florida table.
- Work by pattern. One payer, one reason code, one quarter, one claim list, one letter. That's the version that pays. The method.
- Fix the source. Every repeated denial has an upstream cause: a template, a registration step, a payer table. The recovery is the by-product; the fix is the point.
Prevention or recovery?
Both, in that order. Cleaner claims going out is the cheapest money there is. But prevention only touches claims from today forward. The denials already sitting in closed claims, inside their windows, are a separate pool, and it's usually larger than a year of prevention gains. That pool is what denial recovery is for.
Questions people ask
What are the most common medical billing denials?
Registration and eligibility errors, missing or mismatched authorizations, and coding or bundling edits make up the majority. Experian's 2025 survey named missing or inaccurate claim data and authorization as the top two causes.
What percentage of medical claims are denied?
Roughly 10 to 15 percent on first submission. Experian measured 11.8 percent industry-wide in 2024; Premier's provider survey found nearly 15 percent of claims to private payers.
Which denials are worth appealing?
The administrative ones: registration, authorization on file, coding and bundling with documentation, and timely filing with proof. Premier found private payers overturned more than 60 percent of denials providers fought.