Top 10 Claim Denial Reasons (And How to Fix Each One)

By Ajay Pillai, CEO, Aayur Solutions· June 6, 2026· 9 min read

Claim denials cost the US healthcare system an estimated $20–50 billion annually (MGMA / Kodiak Group). For an individual practice, that translates to $25–$118 in administrative cost to rework each denied claim — plus the revenue risk if appeals aren't filed in time. The national average denial rate is 11.6% (Premier Inc., 2025), but practices with disciplined front-end processes consistently achieve rates below 5%.

The good news: 90% of denials are preventable (CAQH Index 2025). This guide breaks down each of the top 10 denial reasons, explains exactly why they happen, and gives you the specific operational fix for each one.

Top 10 Denial Reasons: Benchmark Data Table

The table below shows each denial category's typical share of total denials, average rework cost, and whether it's preventable at the front end or requires back-end intervention.

Sources: MGMA DataDive 2026; CAQH Index 2025; Premier Inc. 2025. Percentages represent share of total denial volume; ranges vary by specialty and payer mix.

1. Eligibility / Coverage Not Active

What it is: The patient's insurance was inactive, lapsed, or different from what was recorded at the time of service.

Why it happens: Eligibility is verified at registration and never again — or verified once for a new patient and assumed to carry forward for follow-up visits.

Fix: Run real-time eligibility verification on every patient, every visit, the morning of the appointment. Most PM systems support automated batch checks the night before. Use them.

2. Missing or Invalid Prior Authorization

What it is: The procedure required prior authorization and either none was obtained, or the authorization number is wrong/expired.

Why it happens: Authorization is requested after scheduling rather than before confirming the appointment. Or the authorization is obtained but not linked correctly to the claim.

Fix: No confirmed appointment for an authorization-required procedure until the auth number is in the chart. Train front desk and scheduling staff on payer-specific auth requirements by CPT code.

3. Duplicate Claim

What it is: The same claim was submitted more than once for the same date of service, patient, and procedure.

Why it happens: Manual resubmission errors, clearinghouse resubmissions without correcting the original, or PM system configuration issues.

Fix: Review your claim submission workflow to prevent resubmission of claims that are already in "pending" status. Duplicate claim denials should be zero — they indicate a process error, not a payer issue.

4. Coordination of Benefits (COB) Issues

What it is: The patient has multiple insurance policies and the primary vs. secondary payer order is wrong or unknown.

Why it happens: COB information is captured at registration but not verified or updated. Life changes — marriage, job changes, Medicare enrollment — change COB status.

Fix: Verify COB during eligibility checks, especially for Medicare + commercial patients. When COB is unclear, call the payer before submitting rather than guessing the order.

5. Non-Covered Service

What it is: The payer doesn't cover the procedure for this patient's plan, even if the procedure is medically appropriate.

Why it happens: Coverage is not verified at the procedure level — only at the patient level. A patient with active coverage can still have non-covered procedures.

Fix: Verify benefits at the procedure level for high-cost, specialty, or frequently denied services. Collect patient responsibility upfront when coverage is limited or uncertain.

6. Coding Errors (CPT / ICD-10 Mismatch)

What it is: The diagnosis code doesn't support the procedure billed, or the CPT code is wrong, unbundled incorrectly, or missing required modifiers.

Why it happens: Outdated code sets, insufficient provider documentation, coder error, or PM system issues mapping charges to codes.

Fix: Run regular coding audits — at minimum quarterly. Use a claim scrubber that validates CPT/ICD-10 linkage. Address documentation issues with providers directly; coding errors that come from chart documentation cannot be fixed at the biller level.

7. Timely Filing Exceeded

What it is: The claim was submitted after the payer's filing deadline from the date of service.

Why it happens: Claims sit in work queues, get lost in system transitions, or are held for documentation that takes too long to obtain. Timely filing denials are uniquely bad because they are almost never appealable.

Fix: Set a workflow rule: any claim not submitted within 15 days of service date triggers an alert. Know each payer's timely filing window and track submissions accordingly. Most major payers allow 90–180 days; Medicare allows 12 months.

8. Patient Not the Insured / Wrong Policy Holder

What it is: The claim was submitted under the wrong member ID, or the patient's demographic information doesn't match payer records.

Why it happens: Errors at registration — incorrect DOB, name spelling, or policy number. These look minor but produce hard denials.

Fix: Verify member ID and demographics against the insurance card at every visit, not just new patient registration. A patient whose name is "Elizabeth" on the card should not be entered as "Beth."

9. Lack of Medical Necessity

What it is: The payer determines the procedure wasn't medically necessary based on the documentation submitted.

Why it happens: Insufficient clinical documentation, missing diagnosis codes that establish medical necessity, or procedures billed at a level not supported by the documented encounter complexity.

Fix: Work with providers to ensure documentation supports the level of service billed. For high-risk procedures, review medical necessity criteria before submission. These denials require clinical involvement to resolve — billing staff alone cannot fix them.

10. Credentialing / Provider Not in Network

What it is: The rendering provider is not credentialed with the payer, or is credentialed under a different NPI or effective date than what's on the claim.

Why it happens: New providers see patients before their credentialing is complete. Or a credentialing update (new NPI, address change, group reassignment) was not processed correctly.

Fix: Never schedule a new provider to see insured patients before their credentialing is confirmed active. Run a credentialing audit for all providers every 6 months. Track effective dates and re-credentialing timelines proactively.

How to Prioritize: The 90-Day Denial Analysis Method

Don't try to fix all 10 denial reasons at once. That approach produces no results. Instead, use this three-step method that works consistently across practices of any size:

1. Pull 90 days of remittances — export every denied claim with its CARC/RARC codes from your practice management system or clearinghouse.
2. Sort by dollar volume, not count — a denial reason that hits 50 claims at $40 each ($2,000) matters less than one hitting 10 claims at $800 each ($8,000). Prioritize by total revenue impact.
3. Identify your top three categories — in virtually every practice, three denial reason groups account for 70–80% of total denial spend. Fix those three before touching anything else.

Once you've identified your top three, map each to the responsible workflow step. Eligibility failures trace to the front desk. Auth denials trace to scheduling. Coding denials trace to either the provider's documentation or the biller's code selection. Each root cause has a different owner and a different fix.

What a Good Denial Rate Looks Like by Specialty

The 11.6% national average masks significant variation by specialty. Here are 2026 benchmark denial rates by specialty type:

Sources: MGMA DataDive 2026; Premier Inc. 2025. Rates represent initial submission denial rates before appeals.

When to Escalate vs. Write Off a Denied Claim

Not every denial is worth appealing. Use this decision framework before routing a denied claim to your appeals team:

• Always appeal: Medical necessity denials with solid clinical documentation; prior auth denials where auth was obtained but linked incorrectly; credentialing denials where the provider was credentialed but not yet updated in payer system.
• Appeal selectively: Coding denials where the code was clinically supported but not documented — requires provider addendum. Success rate: 40–60%.
• Consider write-off: Timely filing denials beyond the appeal window; duplicate denials where the original was actually paid; COB denials where patient secondary coverage cannot be established.

Industry data shows a 60–80% appeal overturn rate is achievable with systematic denial management. Most practices achieve 20–30% — the gap represents recoverable revenue.

Frequently Asked Questions