The Denial Prevention Playbook
Working denials after the fact is slow and expensive. Stopping them before a claim ever leaves your office is where the real money is. This issue explains how denials work, how to read the codes, and how to build a process that prevents them.
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From the desk. Last month we covered credentialing. This month we move one step down the revenue cycle to the problem every practice feels: denied claims.
Our goal isn’t a better appeal letter. It’s fewer claims that need one — and a clear process for the ones that still slip through.
At a glance
- Most denials start at the front end: registration, eligibility and authorizations.
- Learn to read the group code (CO, PR, OA, PI) and the CARC before touching a denied claim.
- Fix the process, not just the claim — tag every denial with a root cause.
- Know your appeal deadlines: Medicare redeterminations must be filed within 120 days.
- Track denial rate, clean claim rate and recovery rate every month.
Regulatory & industry watch
Claims with dates of service on or after October 1, 2026 must use the FY2027 ICD-10-CM code set. Deleted or expanded codes are a common source of rejections in October and November. Make sure your EHR, superbills and claim scrubber are updated, and that coders know which codes changed in your specialty.
Under CMS’s Interoperability and Prior Authorization final rule, impacted payers — Medicare Advantage, Medicaid and CHIP programs, and ACA marketplace plans — have been required since January 1, 2026 to decide standard prior authorization requests within 7 calendar days and expedited requests within 72 hours, and to give a specific reason when they deny. Prior authorization APIs follow in 2027. If those plans are missing deadlines, document it.
A Medicare redetermination must be filed within 120 days of receiving the initial determination, and a reconsideration within 180 days of the redetermination decision. Commercial payer deadlines are set by contract and are often shorter. Our medical claim appeal guide covers each level.
01Prevention beats appeals
Every denial costs staff time to research, correct and resubmit — and some denied claims are never reworked at all.
Industry analyses consistently find that the majority of denials are preventable, and that a meaningful share of denied claims are simply written off because no one had time to work them. That makes the front end of your revenue cycle — scheduling, registration, eligibility and charge capture — the most valuable place to invest.
It also helps to separate two terms that are often confused. A rejection happens before the payer accepts the claim, usually at the clearinghouse, because of a formatting or data error; it can be corrected and resubmitted quickly. A denial happens after the payer has processed the claim and decided not to pay it. Denials require a corrected claim or an appeal. Our guide to denied vs. rejected claims and our clearinghouse rejection codes list explain both.
02How to read a denial
Every denied line on an ERA or EOB comes with a group code and a Claim Adjustment Reason Code (CARC), and often a Remittance Advice Remark Code (RARC) that adds detail. Reading all three before you act saves a lot of wasted rework.
| Group code | Meaning | Can you bill the patient? |
|---|---|---|
| CO | Contractual obligation | No — the provider is responsible for the adjustment |
| PR | Patient responsibility | Yes — deductible, coinsurance, copay or non-covered service |
| OA | Other adjustment | Depends on the reason code |
| PI | Payer-initiated reduction | Generally no |
The CARC tells you why. CO-16, for example, means the claim is missing information; CO-29 means the filing deadline has passed. Each one points to a different fix — and to a different step in your process that needs attention. We have detailed guides for many of the most common codes, linked in the table below.
03The denials to fix first
| Denial (common CARC) | Typical cause | Prevention step |
|---|---|---|
| Eligibility / coverage (CO-27) | Insurance changed or terminated since the last visit | Verify eligibility before every visit, not just for new patients |
| Prior authorization (CO-197) | Service required auth that wasn’t obtained or had expired | Auth checklist by payer and CPT, checked at scheduling |
| Missing / invalid data (CO-16) | Errors in member ID, DOB, NPI or referring provider | Registration double-check plus claim scrubber edits |
| Diagnosis mismatch (CO-11) | Diagnosis doesn’t support the procedure billed | Coder review and current ICD-10-CM references |
| Modifier issues (CO-4) | Missing or incorrect modifier | Scrubber rules for common modifier pairs |
| Bundling (CO-97) | Service considered part of another service paid | NCCI edit checks; correct modifier use when supported |
| Duplicate (CO-18) | Claim resubmitted instead of corrected or followed up | Check claim status before resubmitting |
| Timely filing (CO-29) | Claim submitted or corrected after the deadline | Payer deadline table and an aging work queue |
For a broader view of why claims are denied and what each pattern says about your billing process, see 10 reasons insurance companies deny claims.
04Build a front-end firewall
Think of the front end as three checkpoints. Each one catches a different kind of error before it turns into a denial.
Checkpoint 1: At scheduling
Capture complete insurance details, confirm the provider is in-network for that specific plan, and flag any service on your authorization list. If an authorization is needed, start it now — not the day before the visit. Our guide on retro authorization explains why “we’ll get it afterward” rarely works.
Checkpoint 2: At check-in
Re-verify eligibility, scan the front and back of the insurance card, confirm demographics and coordination of benefits, and collect the patient responsibility you already know about. Small typos in a member ID or date of birth are among the most common causes of denials. See our best practices to prevent eligibility errors.
Checkpoint 3: Before submission
Run every claim through scrubber edits and hold anything that fails. Check diagnosis-to-procedure logic, modifiers and NCCI edits. A rejection caught in-house costs minutes; a denial from the payer can cost weeks. Accurate medical coding and a well-trained front office are the two biggest levers here.
05Example: fixing a modifier denial
The visit: An established patient comes in for follow-up of diabetes and hypertension. During the same visit, the physician also gives a knee joint injection (CPT 20610). The claim is billed as 99214 + 20610.
The denial: The payer pays the injection but denies the office visit as bundled (CO-97) — some payers use CO-4 for the same issue. The E/M visit was missing modifier 25.
The fix: The coder checks the note and confirms the E/M work was significant and separately identifiable from the injection (the diabetes and blood-pressure management). Modifier 25 is appended to 99214 and a corrected claim is submitted. For commercial plans, that’s typically a replacement claim (frequency code 7) with the original claim number. For Medicare Part B, corrections are usually handled through the MAC’s reopening process instead.
The prevention: A scrubber rule now flags any E/M billed on the same day as a minor procedure without modifier 25, so a coder reviews it before it goes out.
Modifier 25 should only be used when documentation supports it — overuse is an audit risk. Our 99214 billing guide covers the documentation requirements.
06When a denial still lands
No process is perfect. When a denial arrives, a consistent workflow keeps it from aging out:
- Read the codes first — group code, CARC and RARC — before touching the claim.
- Sort into correctable vs. appealable. A corrected claim is often faster than a formal appeal.
- Check the deadline for that payer and work the oldest, highest-dollar items first.
- Gather supporting documents — notes, authorizations, eligibility screenshots — before writing the appeal.
- Tag every denial with a root cause so trends become visible, not just individual claims.
- Follow up on every appeal until a decision is received.
Our step-by-step denied claims workflow walks through each stage. If your team doesn’t have the time, outsourcing denial management can clear the backlog and fix the root causes.
07Metrics worth tracking
You can’t improve what you don’t measure. Review these monthly, by payer:
| Metric | How to calculate | Why it matters |
|---|---|---|
| Denial rate | Denied claims ÷ claims submitted | The headline number; many practices aim for under 5% |
| Clean claim rate | Claims accepted first time with no edits ÷ total claims | Shows how well your front-end process works |
| Top denial reasons | Denials grouped by CARC and payer | Shows where process fixes will pay off most |
| Overturn rate | Appeals won ÷ appeals filed | Shows whether appeals are well-prepared |
| Recovery rate | Denied dollars collected ÷ denied dollars | Shows how much denied revenue is really recovered |
Frequently asked questions
What’s the difference between a denied claim and a rejected claim?
A rejected claim never made it into the payer’s system, usually because of a formatting or data error caught by the clearinghouse or payer front end. It can be fixed and resubmitted. A denied claim was processed and the payer decided not to pay; it needs a corrected claim or an appeal.
Should we resubmit or appeal a denied claim?
If the denial was caused by an error on your side (a missing modifier, wrong code or typo), submit a corrected claim. If you believe the claim was correct and the payer made the wrong decision, file an appeal with supporting documentation. Never send the same claim again unchanged — it will usually deny as a duplicate.
How long do we have to appeal?
For Medicare, a redetermination must be filed within 120 days of receiving the initial determination. Commercial and Medicaid deadlines vary by payer and contract and are often shorter, so keep a deadline table for each payer.
Can we bill the patient for a denied claim?
It depends on the group code. Denials with a CO (contractual obligation) group code generally cannot be billed to the patient. PR (patient responsibility) amounts can. Check your payer contracts and our guide to patient balance billing rules.
What is a good denial rate?
Many practices aim to keep their denial rate under 5%, though it varies by specialty and payer mix. The trend over time, and the reasons behind it, matter more than a single number.
Key dates & rules to remember
| Rule | Timeframe |
|---|---|
| FY2027 ICD-10-CM code set | Effective October 1, 2026 |
| Medicare redetermination (level 1 appeal) | Within 120 days of the initial determination |
| Medicare reconsideration (level 2 appeal) | Within 180 days of the redetermination |
| Prior auth decisions (impacted federal payers) | 72 hours expedited / 7 calendar days standard |
| Medicare timely filing | 12 months from date of service |
Related resources
This newsletter is for general information only and is not legal, coding or compliance advice. Payer rules vary — always confirm requirements with the payer or your MAC.
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