Top Claim Denial Reasons and How to Prevent Them
The most common reasons insurance claims are denied, what the denial codes mean, and practical steps your practice can take to prevent them.
By AccMed RCM Team · Medical Billing Guides
Every denied claim costs a practice twice: once in delayed or lost revenue, and again in the staff time needed to fix and resubmit it. The good news is that most denials come from a short list of repeat causes, and most of those can be prevented before the claim ever leaves your office. This guide covers the most common denial reasons, how to read denial codes and the habits that keep denials down.
How to read a denial
Each denied line on an ERA or EOB carries a Claim Adjustment Reason Code (CARC) that explains why the payer adjusted or denied it, and often a Remittance Advice Remark Code (RARC) with more detail. A group code — such as CO (contractual obligation) or PR (patient responsibility) — tells you who is responsible for the amount. Reading all three together tells you whether to correct the claim, appeal it or bill the patient.
The most common denial reasons
| Denial reason | Typical cause | How to prevent it |
|---|---|---|
| Eligibility or coverage | Inactive coverage, wrong plan or wrong payer | Verify eligibility before every visit, including secondary coverage |
| Missing prior authorization | Service needed approval that was not obtained or had expired | Check authorization rules when the service is ordered and track expiration dates |
| Coding errors | Wrong CPT or ICD-10 code, or codes that do not support each other | Code from documentation and scrub claims against payer edits |
| Missing or wrong modifier | 25, 59, X{EPSU}, 26/TC or therapy modifiers missing or misused | Build modifier rules into your claim scrubber |
| Medical necessity | Diagnosis does not meet the payer’s coverage policy | Check LCDs and payer policies; improve documentation |
| Timely filing | Claim submitted after the payer’s deadline | Submit claims promptly and track rejections daily |
| Duplicate claim | Same service submitted twice, often during follow-up | Check claim status before resubmitting |
| Credentialing | Rendering provider not enrolled with the payer | Keep a credentialing roster and track effective dates |
Rejections vs denials
A rejection happens before the payer accepts the claim — usually at the clearinghouse — because of missing or invalid data such as a wrong member ID or NPI. Rejected claims were never received, so they must be fixed and resubmitted quickly or they can run out of filing time. A denial means the payer received and processed the claim and decided not to pay all or part of it.
Seven habits that prevent denials
- Verify eligibility one to three days before each visit and again for walk-ins.
- Track authorizations with approved units and expiration dates.
- Scrub every claim for coding, modifier and NCCI edits before submission.
- Work rejections daily so they never become timely-filing denials.
- Group denials by root cause every month, not just by payer.
- Give providers documentation feedback on the codes that deny most.
- Keep credentialing current for every provider and location.
What a healthy denial rate looks like
Many practices aim to keep their initial denial rate in the single digits. If more than about one claim in ten is denied, there is usually a fixable pattern — often eligibility, authorization or a recurring coding issue. Our denial management services find and fix those root causes.
When to appeal
Appeal when the service was correctly billed and medically necessary but the payer still denied it. Use a corrected claim instead when the denial was caused by your own error, such as a wrong code or modifier. Track every appeal deadline — Medicare allows 120 days from the initial determination to request a redetermination, while commercial plans set their own limits.