Top 7 Reasons Medical Claims Get Denied (And How to Fix Them)

Claim denials are the most expensive — and most preventable — failure mode in U.S. medical billing. Industry research from Change Healthcare shows that 86% of denials are avoidable, yet the average practice still operates with a denial rate of 5–10% and a first-pass appeal success rate below 60%.

Across thousands of audited claims, denials cluster into a small set of repeat offenders. Eliminate these seven categories and most practices see their denial rate fall below 4% within 90 days — typically worth 3–6% in net collections.

1. Missing or Invalid Patient Information

The cause

Demographic and insurance data captured at registration contains errors — wrong policy number, transposed digits in the date of birth, outdated address, or invalid subscriber relationship. This category accounts for roughly 27% of all initial denials.

The impact

These claims are usually rejected by the clearinghouse or denied with reason codes 16, 31, or 140. Each one adds 14–21 days to AR and consumes 15–20 minutes of staff time to correct and resubmit.

The fix

• Run real-time eligibility verification at scheduling and again 48 hours before service.
• Use standardized intake scripts and require front-desk staff to read back key fields.
• Implement automated demographic-verification tools integrated with your EHR.

2. Eligibility & Coverage Issues

The cause

The patient's coverage was inactive on the date of service, the service is not a covered benefit, or the patient hit a benefit limit. Roughly 18% of denials fall here, and they are nearly all preventable.

The impact

Often results in 100% balance shifting to the patient — which has a collection rate of under 30% once the bill is post-service. Direct revenue loss.

The fix

• Mandatory eligibility check within 48 hours of every encounter.
• Train staff to read 271 responses for benefit limits, not just active/inactive status.
• Provide patient-responsibility estimates and collect at point of service.

3. Missing or Invalid Prior Authorization

The cause

The service required prior auth and either none was obtained, the auth was for a different CPT, or the auth expired before the service was rendered. This category is growing fastest, currently around 13% of denials and rising every year.

The impact

Most prior-auth denials become full write-offs because payers do not allow retroactive authorization. Single high-dollar services (imaging, infusions, surgery) can cost $1,500–$15,000 each.

The fix

• Maintain a payer-specific authorization matrix updated quarterly.
• Use auth tracking software with expiration alerts.
• Build a hard-stop in scheduling for any CPT requiring auth before booking.

4. Coding Errors and Insufficient Documentation

The cause

Codes are wrong, downcoded, missing modifiers, or unsupported by clinical documentation. Modifier-25 misuse, lack of medical necessity, and bundled-code confusion lead this list. Approximately 11% of denials are coding-related.

The impact

Beyond rework cost, coding errors carry compliance risk and can trigger payer audits. Underpayment from chronic downcoding is harder to detect and often persists for years.

The fix

• Use AAPC- or AHIMA-certified coders, not generalists.
• Run quarterly coding audits sampling 30+ claims per provider.
• Implement provider-level documentation feedback loops within 30 days of denial.

5. Duplicate Claims and Timely Filing

The cause

Either the same claim was submitted twice (often after staff loses track of original submission) or the claim was submitted after the payer's filing window closed. Together these account for around 9% of denials.

The impact

Timely-filing denials are nearly always non-appealable — the revenue is permanently lost. For practices with weak AR processes, timely-filing write-offs can exceed $50,000 per year.

The fix

• Maintain a payer-specific timely-filing calendar and aging report cutoffs.
• Submit all claims within 72 hours of date of service.
• Run weekly aging reports and escalate any claim approaching 75% of filing window.

6. Coordination of Benefits (COB) Issues

The cause

The patient has multiple insurance plans and the wrong primary was billed, or COB information on file with the payer is outdated. Around 7% of denials.

The impact

Adds 30–60 days to AR while patient and payers reconcile coverage order. Often results in patient frustration and balance disputes.

The fix

• Ask every patient at every visit about additional coverage — not just at intake.
• Verify Medicare Secondary Payer questionnaire compliance for every Medicare patient.
• Build a quick COB-update workflow that triggers a patient call rather than a write-off.

7. Medical Necessity & Non-Covered Services

The cause

The payer does not consider the diagnosis-procedure pairing medically necessary, or the service is excluded from the patient's plan. Roughly 6% of denials.

The impact

Often appealable with strong clinical documentation, but only if the practice catches it quickly and has the supporting records ready. Many are written off out of inertia.

The fix

• Maintain payer-specific LCD/NCD lookup at the point of order.
• Use Advance Beneficiary Notices (ABNs) appropriately to shift liability.
• Build appeal templates for the top 10 medical-necessity denial reasons by payer.

The Compounding Effect

Each denial category looks small in isolation. Stacked together, they explain why average practices operate at 88–92% net collection rates while top-decile practices clear 96%+. That four-point gap on a $4M practice is $160,000 per year — the difference between hiring another provider and barely covering overhead.

Build a Denial Management Function, Not a Denial Cleanup Function

Most practices treat denials as cleanup work. Top performers treat denials as root-cause data. Every denial is an instruction from the payer about how to submit better next time. The right operating model categorizes denials by reason code, tracks them by payer and by provider, and feeds the analysis back into front-end workflow every single week.

Our denial management services do exactly this — combining same-day appeals with structural prevention. To see what is possible at scale, read the case study: Mental Health Practice Cuts Denial Rate from 14% to 4%.

For a broader view of how denial management fits into the full revenue cycle, see our companion guide: What is Revenue Cycle Management?