The most common medical billing denials are eligibility errors, missing or invalid claim data, missing prior authorization, non-covered services, and medical necessity. Coding errors, bundling edits, duplicates, coordination of benefits, and timely filing round out the top 10. Most are preventable at the front end, before the claim leaves your system.
Claim denial statistics for 2026
40% of providers say at least 1 in 10 claims is denied, and 75% say denials are increasing (Experian Health State of Claims, October 2026; 204 respondents).
Services not covered is the most-cited denial reason (53% list it in their top three), followed by changing payer policies (31%), then coding errors and prior authorization (25% each).
10.63% was the average initial denial rate in the first half of 2026, down from 12.00% a year earlier (Kodiak Solutions, 2,400 hospitals and 375,000 physicians).
Takebacks rose 13.8%, to 1.57% of accounts receivable, so lower denials didn't translate into more cash.
Medicare Advantage initial inpatient denials ran at 9.15%, more than double traditional Medicare's 4.21%.
Denial vs rejection: know which one you have
A rejection fails front-end edits at the clearinghouse or payer and is never processed. Fix it and submit it as a new claim. A denial was processed and refused payment. Fix it with a corrected claim (frequency code 7) or an appeal, not a fresh submission, or you'll trigger a duplicate denial.
How to read denial codes
Every denial on an 835 or paper remittance carries a group code plus a Claim Adjustment Reason Code (CARC), often with a Remittance Advice Remark Code (RARC) giving detail.
Group code | Meaning | Who owes it |
|---|---|---|
CO | Contractual obligation | Provider; can't bill the patient |
PR | Patient responsibility | Patient |
OA | Other adjustment | Depends on the reason |
PI | Payer-initiated reduction | Provider, usually |
CO-45 (charge exceeds the fee schedule) and PR-1, PR-2, PR-3 (deductible, coinsurance, copay) are normal adjustments, not denials. Don't count them in your denial rate.
The top 10 claim denials
# | Denial | Common CARCs | Typical root cause | Fix |
|---|---|---|---|---|
1 | Eligibility and registration errors | CO-27, CO-26, CO-31, CO-109 | Coverage ended, wrong member ID or DOB, wrong payer | Verify eligibility at scheduling and again before the visit; update demographics; rebill the correct payer |
2 | Missing or invalid claim data | CO-16 (plus a RARC) | Missing NPI, referring provider, NDC, or invalid place of service | Read the RARC, correct the field, send a corrected claim |
3 | No prior authorization | CO-197, CO-15 | Auth not obtained, expired, or not linked to the claim | Build an auth matrix by payer and CPT; attach auth numbers; request retro-auth where allowed |
4 | Service not covered | CO-96, CO-204 | Excluded benefit or plan limit | Check benefits before service; get a signed ABN or waiver so the patient can be billed |
5 | Medical necessity | CO-50, CO-167 | Diagnosis doesn't meet NCD/LCD or payer policy | Code to highest specificity; check coverage policies; appeal with records |
6 | Coding and modifier errors | CO-4, CO-11, CO-181, CO-182 | Deleted codes, wrong modifier, diagnosis-procedure mismatch | Update code sets every January and October; run a claim scrubber |
7 | Bundling and NCCI edits | CO-97, CO-236 | Component billed with comprehensive code; modifier 59 or X{EPSU} unsupported | Check NCCI and payer edits; use modifiers only when documentation supports a distinct service |
8 | Duplicate claim | CO-18 | Resubmitting instead of correcting; double charge entry | Use frequency code 7 for corrections; check claim status before resending |
9 | Coordination of benefits | CO-22 | Another payer is primary, or the payer's COB file is outdated | Ask about other coverage at every visit; have the patient update COB with the payer |
10 | Timely filing | CO-29 | Claim sent or corrected after the payer's deadline | Track deadlines by payer; keep clearinghouse acceptance reports as proof |
Timely filing limits to know
Medicare allows 12 months from the date of service. Commercial payers often allow 90 to 180 days, and Medicaid varies by state, so keep a payer-by-payer table in your billing system.
A three-stage denial prevention workflow
Front end (scheduling to check-in): real-time eligibility, benefits and authorization checks, accurate demographics, and COB questions. This stage drives roughly half of all denials.
Mid-cycle (charge capture to submission): coding to the current code set, documentation that supports medical necessity, and a scrubber with payer-specific edits.
Back end (remittance to resolution): work denials within days, categorize each by root cause, appeal with evidence, and feed patterns back to the front desk and coders every month.
Denial KPIs and benchmarks
Metric | What it measures | Target |
|---|---|---|
Initial denial rate | Claims denied on first submission | Under 5% |
Final denial rate | Charges written off after appeals | Under 2% |
Clean claim rate | Claims paid on first pass without edits | 95% or higher |
Denial overturn rate | Appealed denials that get paid | Track by payer and reason |
Takeback rate | Paid dollars recouped later | Track monthly; rising in 2026 |
How to appeal a denial
Read the CARC and RARC together; the RARC often names the missing item.
Decide: corrected claim (data or coding error) or appeal (you disagree with the payer's decision).
For appeals, cite the payer policy or LCD, attach records that prove necessity, and file before the deadline.
Medicare appeals move through five levels, starting with redetermination by the MAC.
Log the outcome so you can measure overturn rates by payer and reason.
FAQ
What is the most common denial in medical billing?
Eligibility and registration errors have led industry denial indexes for years. In Experian's 2026 survey, providers most often named services not covered among their top three reasons.
What is a CO-16 denial?
The claim lacks information or has a submission or billing error. Check the RARC to see which field is missing, fix it, and send a corrected claim.
What is a good denial rate?
Under 5% initial and under 2% final. The 2026 industry average for initial denials was about 10.6%.
Is CO-45 a denial?
No. It's a contractual adjustment showing your charge exceeded the allowed amount.
How much does a denial cost to rework?
Industry estimates put administrative rework at roughly $25 to $60 or more per claim, before counting lost revenue on claims never resubmitted.
Sources: Experian Health State of Claims 2026 · TechTarget on Kodiak's first-half 2026 analysis · Healthcare Finance News on 2026 takebacks · HealthLeaders on Kodiak's 2025 data · Luxen denial benchmarks
