Common claim denial types, and how to appeal each one
Most denials trace back to a handful of recurring reasons. Here's what each one means, the code behind it, and what actually overturns it. Pick the denial you're fighting.
Modifier 25
A Modifier 25 denial happens when you bill a significant, separately identifiable E/M service on the same day as a procedure, and the payer decides the E/M wasn't separate and bundles it into the procedure.
How to appeal it →Medical Necessity
A medical necessity denial means the payer decided the service wasn't medically necessary for the patient under its coverage policy, even though it was performed and documented.
How to appeal it →Timely Filing
A timely filing denial means the claim was received after the payer's filing deadline. It's the denial practices most often write off, and the one most often recoverable with proof.
How to appeal it →Prior Authorization
A prior-authorization denial means the payer says the required pre-approval wasn't obtained before the service. It's common, and a large share are recoverable.
How to appeal it →Bundling / NCCI Edits
A bundling denial means the payer applied an NCCI edit and folded one procedure into another, paying only the primary code even though both services were performed.
How to appeal it →Missing or Invalid Information
This denial means the claim is missing or has invalid information the payer needs to adjudicate it, from a member ID to a required modifier or referring provider.
How to appeal it →Coordination of Benefits
A coordination-of-benefits (COB) denial means the payer believes another plan is primary, or the patient's COB information is out of date, so it won't pay until the order is resolved.
How to appeal it →Non-Covered Service
A non-covered denial means the payer says the service isn't a covered benefit under the patient's plan. Some are truly non-covered; many are mis-categorized or mis-coded.
How to appeal it →Duplicate Claim
A duplicate denial means the payer thinks this claim or line was already submitted. Often it's a true duplicate, but frequently it's a distinct service the payer mis-flagged.
How to appeal it →Experimental / Investigational
This denial means the payer considers the service experimental or investigational under its medical policy, so it won't cover it, even when it's the appropriate care.
How to appeal it →Downcoding
A downcoding denial is when the payer pays a lower-level code than you billed, dropping a 99214 to a 99213 or reducing units, often silently, so the claim looks paid even though it was cut.
How to appeal it →Eligibility / Coverage Not in Effect
An eligibility denial means the payer says the patient wasn't covered on the date of service, coverage had ended, hadn't started, or the member couldn't be matched to the plan.
How to appeal it →Referral Required / Absent
A referral denial means an HMO or POS plan won't pay a specialist claim because the required primary-care referral wasn't on file or had run out.
How to appeal it →Diagnosis Inconsistent with Procedure
This denial means the payer says the diagnosis on the claim doesn't support the procedure billed. It's almost always a coding or linkage issue, not a problem with the care.
How to appeal it →Provider Not Eligible / Credentialing
This denial means the payer says the rendering provider wasn't eligible or credentialed to perform or bill this service on the date of service.
How to appeal it →Global Surgery Period (E/M During Global)
This denial bundles an office visit into a procedure's global surgical period, treating it as included post-op care, even when it was a separate, billable service.
How to appeal it →Frequency / Units Exceeded (MUE)
This denial rejects units above a frequency limit or a Medically Unlikely Edit (MUE), paying some units on the line and denying the rest.
How to appeal it →Step Therapy / Fail-First
A step-therapy or fail-first denial means the payer won't cover the drug or treatment you ordered until the patient has tried and failed a cheaper preferred option first, even when the clinical case for going straight to your choice is strong.
How to appeal it →Site of Service
A site-of-service denial means the payer decided the procedure should have been done in a lower-cost setting, or that the place-of-service code doesn't match where the payer thinks the service belonged, so it denies or reprices the claim.
How to appeal it →Telehealth POS / Modifier
A telehealth denial means the payer rejected a virtual visit because the place-of-service code (02 or 10) or the telehealth modifier (95, GT, GQ, FQ) didn't match the payer's current telehealth rules, which have shifted repeatedly since the public-health-emergency changes.
How to appeal it →Auth on File but Still Denied
This is the auth denial that shouldn't exist: you obtained the prior authorization, the number is on file, and the payer denied the claim anyway because the auth wasn't linked, the codes didn't match, or the payer's own system lost it.
How to appeal it →Out-of-Network / Network Status
A network-status denial means the payer processed your claim as out-of-network, or denied it for network reasons, even though the provider is contracted, usually because credentialing hadn't loaded yet or the claim routed to the wrong contract.
How to appeal it →Assistant Surgeon
An assistant-surgeon denial means the payer says an assistant wasn't payable for this procedure, either because its policy doesn't allow one for the code, or the assistant modifier (80, 81, 82, or AS) didn't match the assistant's role.
How to appeal it →New vs Established Patient
This denial means the payer rejected a new-patient E/M code (99202-99205) because its records show the patient was seen within the prior three years, so it considers them established, even when the three-year rule or same-specialty-same-group test actually supports the new-patient level.
How to appeal it →Drug / J-Code Units
A drug or J-code denial means the payer rejected a buy-and-bill drug claim because the billed units didn't match the code's dosage definition, exceeded a limit, or the J-code and NDC didn't line up, which is easy to get wrong because J-code units rarely equal milligrams given.
How to appeal it →Screening vs Diagnostic
This denial means the payer processed a service under the wrong benefit, applying cost-sharing or denying a screening because it was coded diagnostic, or denying a diagnostic service billed as screening, most visibly on colonoscopies and other preventive-to-diagnostic conversions.
How to appeal it →LCD / NCD (Medicare Coverage Policy)
An LCD/NCD denial means Medicare or a Medicare Advantage plan denied the service because the diagnosis or circumstances didn't meet a Local or National Coverage Determination, the specific, published rules that define when Medicare covers a service.
How to appeal it →Documentation Insufficient
A documentation-insufficient denial means the payer says the records it received don't support the service billed, either because nothing was attached, the wrong note went in, or the documentation didn't reach the level of detail the payer wanted.
How to appeal it →Corrected Claim Denied as Duplicate
This denial happens when you fix and resubmit a claim and the payer, instead of replacing the original, reads the corrected claim as a duplicate and denies it, so your correction never gets adjudicated and the fix is lost.
How to appeal it →Not sure which denials are recoverable?
A free assessment shows your real recoverable number across every denial type. No risk, paid only on what we recover.
Get your free assessment →