How to Appeal an Insurance Denial
Your insurance company denied your claim. That feels like a final answer — but it may still be reviewable. Start by getting the denial reason, plan language, dates, and missing documents in one place.
THE SHORT VERSION
- 1. Read your denial letter — find the denial code and reason
- 2. Request your full claim file from the insurer
- 3. Verify the deadline in the denial notice and plan documents, then submit on time
- 4. If internal appeal fails, request an external review (independent third party)
- 5. Escalate to your state insurance commissioner if needed
Reading your denial code is free. The finished appeal, written against that specific reason with your plan's deadlines counted out, is $19 once — no subscription and no account.
→ Skip ahead: decode my denial freeIN THIS GUIDE
- 1. Why Claims Get Denied and What to Verify
- 2. Understanding Your Denial Letter
- 3. Step 1: File an Internal Appeal
- 4. Step 2: Request an External Review
- 5. Common Denial Codes and How to Beat Them
- 6. Critical Deadlines You Cannot Miss
- 7. What to Say in Your Appeal Letter
- 8. When to Escalate Beyond the Insurer
- 9. FAQ
1. Why Claims Get Denied and What to Verify
Insurance companies deny claims for dozens of reasons, but most fall into a few categories. Understanding why your claim was denied is the first step to overturning it.
Wrong patient info, a missing referral number, an incorrect provider ID, or a duplicate submission may be correctable. Ask which field or record caused the denial.
The plan says the service was not pre-approved. Check the plan terms, emergency-service rules when relevant, and whether the provider or plan has a correction or reconsideration process. Do not assume an after-the-fact approval is available.
The plan says the service was not medically necessary. Ask for the criteria used and compare them with the treating clinician's records and plan language.
The service may be excluded, or the plan may show an eligibility problem. Compare the denial with the coverage document and eligibility record for the service date.
Other denial reasons include coding questions, timely filing, and coordination of benefits. The available correction, reconsideration, or appeal path depends on the plan and denial notice.
Verify the controlling rules in your denial notice, plan documents, state process, and current HealthCare.gov guidance.
2. Understanding Your Denial Letter
Denial notices for many regulated health plans must include reasons and appeal information. Requirements vary by plan type and jurisdiction. Here is what to look for and request if it is missing:
A code like CO-50, PR-1, or N265. This tells you exactly why the claim was denied. Our tool decodes these automatically.
The letter must explain in plain English why the claim was denied. If it's vague ('not medically necessary' with no detail), that itself is grounds for appeal.
Find the submission route and deadline. Many Marketplace and other non-grandfathered plan internal appeals allow at least 180 days, but verify your plan and notice.
Check whether the denial qualifies for an independent external review and which federal or state process applies.
Practical step: If important information is missing, ask the plan in writing for the denial rationale, controlling plan language, appeal instructions, deadline, and any available external-review notice.
3. Step 1: File an Internal Appeal
An internal appeal is reviewed by the insurance company itself — but by a different person than the one who denied your claim. Under ACA §2719, all non-grandfathered health plans must provide at least one level of internal appeal.
How to file:
State the denial reason, ask for the plan language or evidence used, and include your policy number, claim number, date of service, and denial date. Review any draft before sending.
Get a letter of medical necessity from your treating physician. Include medical records, test results, peer-reviewed literature supporting the treatment, and your plan's own coverage criteria showing the service should be covered.
Use the deadline in the denial notice and plan documents. Many Marketplace and other non-grandfathered plan internal appeals allow at least 180 days, while urgent cases may have expedited procedures. Use the plan's submission route and save proof of delivery.
Under ACA §2719(b)(2)(B), you have the right to access and copy your entire claim file, including the clinical rationale used to deny your claim. This often reveals weak reasoning you can challenge directly.
Don't write your appeal letter from scratch
Clever Dispute helps decode denial language and organize review questions. It does not calculate a real win probability or provide legal advice. Decoding the denial is free; the written appeal kit is $19 once.
Decode My Denial Free — Appeal Kit $194. Step 2: Request an External Review
If your internal appeal is denied, you have the right to an external review — an independent third party (not affiliated with your insurer) reviews the decision. This is one of the most powerful protections in the ACA.
Under ACA §2719, after exhausting internal appeals (or simultaneously for urgent cases), you can request that an independent review organization (IRO) evaluate your claim. The IRO is chosen by the state or a federal authority — not your insurer.
External-review rules, eligible denial types, and the effect of a decision depend on the governing federal or state process and plan. Read the notice that comes with the decision and ask the regulator or plan how it will be implemented.
Federal and state external-review windows can differ. Use the internal-appeal decision, plan documents, and regulator instructions. Urgent situations may have an expedited route.
5. Common Denial Codes and What to Verify
Many denial notices include a claim-adjustment or remark code. The label is a starting point, not a complete explanation. Ask the plan which record and rule controlled:
| Code | Meaning | Check | Strategy |
|---|---|---|---|
| CO-50 | Not medically necessary | CRITERIA | Request the criteria used; compare clinician records and plan terms |
| CO-16 | Missing info to adjudicate | RECORDS | Request the specific missing items and the resubmission route |
| N265 | Prior auth required | PLAN | Check authorization records, plan terms, and any applicable emergency rules |
| CO-97 | Bundled with another service | CODING | Ask how the services and modifiers were evaluated under applicable coding edits |
| CO-29 | Filing deadline expired | TIMING | Provide dated proof of submission and ask which deadline was applied |
| CO-18 | Duplicate claim | DATES | Show whether the services were separate encounters or a duplicate submission |
| CO-197 | Missing preauthorization | PLAN | Check authorization records and the plan's correction or appeal process |
| PR-1 | Applied to deductible | EOB | Compare the EOB, deductible ledger, and plan year |
Our denial review tool helps organize common denial-code questions and a draft you can review. It does not calculate a real win rate.
6. Critical Deadlines You Cannot Miss
Missing a deadline can limit appeal options. Mark every date in the denial notice and plan documents, and confirm an urgent or external-review route directly with the plan or regulator:
7. What to Say in Your Appeal Letter
An effective appeal letter is specific, evidence-based, and cites the law. Here's the structure:
State your name, policy number, claim number, date of service, and denial date. Reference the specific denial code and reason language from the denial letter.
Address the specific denial reason with evidence. If 'not medically necessary' — include physician statement and clinical guidelines. If 'not covered' — cite the specific plan benefit that covers it. If admin error — explain the correction.
Cite ACA §2719 (appeal rights), the No Surprises Act (for emergency/out-of-network), your state's insurance regulations, and any applicable specialty guidelines (AMA, ACR, etc.).
List all attachments: physician letter, medical records, peer-reviewed studies, plan documents showing coverage, prior authorization records if applicable.
Request reversal of the denial, reprocessing of the claim, and written confirmation. State your intent to pursue external review and regulatory complaints if the appeal is denied.
Let AI write your appeal letter
Enter your denial code to organize a plain-English appeal review draft. Check your plan documents and deadlines before sending anything. The read is free; the Denial Appeal Kit is $19 once.
Decode My Denial Free — Appeal Kit $198. When to Escalate Beyond the Insurer
If your internal and external appeals fail — or if the insurer is violating the process — you have additional options:
Every state has an insurance commissioner who investigates consumer complaints against insurers. Filing a complaint creates a regulatory paper trail that insurers take seriously. Many denials are reversed at this stage because insurers don't want regulatory scrutiny.
Find yours at naic.org/state-insurance-regulators
For Medicare Advantage plans or ACA marketplace plans, file a complaint at cms.gov/nosurprises. CMS has enforcement authority and can order the insurer to reprocess your claim.
File at cms.gov/nosurprises
If the denied claim has resulted in medical debt or collections activity, the Consumer Financial Protection Bureau can investigate. Particularly effective if the billing is unfair, deceptive, or abusive.
File at consumerfinance.gov/complaint
For patterns of bad faith denial (e.g., the insurer routinely denies a specific treatment that's clearly covered), your state AG's consumer protection division may investigate.
Find yours at naag.org
9. Frequently Asked Questions
Can I appeal a denial after the deadline has passed?+
Do I need a lawyer to appeal an insurance denial?+
What if my employer's plan denied the claim?+
Can the insurer deny my appeal without reviewing new evidence?+
What if my claim is for emergency care?+
Should I pay the bill while I'm appealing?+
Your insurer denied your claim. Build the review record.
Denials can be worth reviewing. Clever Dispute helps you decode the reason, collect the record, and prepare cautious wording before you submit an appeal. Decoding your denial code is free. The Denial Appeal Kit, which writes the internal appeal against that reason and the external review request behind it, is $19 once.
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