Insurance Claim Denied? The Complete Guide to Appealing
Your insurance claim was denied. What now? This guide covers everything — why it happened, what your rights are, the step-by-step appeal process, and the tools that work. Less than 1% of patients appeal, but about 60% of those who do win.
Why Claims Get Denied
Insurance companies deny claims for several standard reasons. Understanding which applies to your case is the first step to an effective appeal.
Not Medically Necessary
The insurer claims the treatment doesn't meet their internal clinical criteria — even if your doctor prescribed it.
Prior Authorization Not Obtained
The treatment required advance approval that wasn't requested, or was requested and denied before treatment.
Out-of-Network Provider
Your provider is outside the plan's network, or an unexpected provider (anesthesiologist, lab) was out-of-network.
Experimental / Investigational
The insurer classifies your treatment as unproven, regardless of specialist consensus.
Pre-existing Condition
The insurer claims your condition predates coverage. ACA plans cannot apply this to marketplace plans.
Documentation Incomplete
Required records, codes, or forms were missing from the claim submission.
Other / Coverage Excluded
The service is explicitly excluded in your policy, or there's a coverage dispute.
Source: ClaimBack platform data (10,847 analyzed denials, 2023–2026)
See the full denial statistics research →
Your Rights When a Claim Is Denied
In most countries, you have strong legal rights when an insurance claim is denied. Insurers are required to explain their decision, provide the criteria used, and give you a path to appeal.
🇺🇸 United States (ACA)
Written denial with reason required. Right to internal appeal. Right to external review by an IRO. External review is binding on the insurer.
🇬🇧 United Kingdom
Right to formal internal complaint. If unresolved within 8 weeks, escalate to Financial Ombudsman Service (FOS) — free and legally binding.
🇦🇺 Australia
Right to internal dispute resolution. Escalate to AFCA (Australian Financial Complaints Authority) — free, decisions binding on insurer.
🇸🇬 Singapore
Right to internal appeal. Escalate to FIDReC (Financial Industry Disputes Resolution Centre) — free for claims up to SGD 100,000.
🇦🇪 UAE
File complaint with Insurance Authority within 60 days of final insurer response. Free process.
🇮🇳 India
Right to approach IRDAI Bima Bharosa portal or the Insurance Ombudsman (free) within 30 days.
See rights for all 100+ countries →
How to Appeal Step by Step
A successful appeal follows a clear sequence. Skipping steps — especially documentation — is the most common reason appeals fail.
1
Get the denial in writing
Request a formal denial letter specifying the exact reason code and policy provision. Your insurer is legally required to provide this.
2
Request your complete claim file
Ask for everything the insurer used to make their decision — including the clinical policy bulletin (CPB) they applied to evaluate medical necessity.
3
Have your doctor write a Letter of Medical Necessity
This letter must directly address the insurer's stated denial reason, cite their own clinical criteria, and reference published clinical guidelines (NCCN, AHA, ADA, etc.).
4
Write your appeal letter
Address each element of the denial reason. Cite your policy language, relevant regulations, and your doctor's supporting evidence. Be specific — vague appeals fail.
5
Submit within the deadline
Internal appeal deadlines are typically 30-180 days from denial (varies by plan type and country). Missing the deadline forfeits your right to appeal.
6
Follow up in writing
Confirm receipt. If the insurer doesn't respond within the required timeframe, note this in writing — it strengthens a subsequent external review or complaint.
7
Escalate to external review if needed
If the internal appeal is denied, you have the right to independent external review in most countries. External reviewers approve about 40% of cases that internal appeals deny.
Appeal Letter Templates
Your appeal letter needs to be specific — citing the insurer's own criteria and the applicable regulations. Generic templates rarely succeed.
The most effective approach: a personalized letter
ClaimBack generates a customized appeal letter for your specific insurer, denial reason, and country — citing the exact regulations and clinical evidence that apply to your case.
Generate My Personalized Appeal Letter — Free →If you prefer to write your own, the key elements are: specific policy citation, your doctor's clinical justification referencing the insurer's criteria, published clinical guidelines (NCCN, AHA, ADA), and a clear request for reconsideration with deadline for response.
When to Escalate: External Review
If your internal appeal is denied, you haven't exhausted your options. External review (also called third-party review or ombudsman complaint) is your next step — and it's free in most countries.
🇺🇸 US (ACA plans)
Request external review through your state insurance commissioner or the federal portal (healthcare.gov/appeal). Independent Review Organization (IRO) makes a binding decision.
🇬🇧 UK
Escalate to the Financial Ombudsman Service (FOS) after exhausting your insurer's internal process. File at financial-ombudsman.org.uk — free.
🇦🇺 Australia
Escalate to AFCA (afca.org.au) — free for consumers. Decisions are legally binding on the insurer.
🇸🇬 Singapore
Escalate to FIDReC (fidrec.com.sg) — free for claims up to SGD 100,000. Binding on insurer if accepted.
Find your country's external review process →
Guides by Insurer
Each insurer has its own clinical policy bulletins, denial patterns, and appeal requirements. Find the guide for your specific insurer:
Browse all insurer guides →
Guides by Condition
Different conditions require different appeal strategies. Find guides with the specific clinical evidence and policy arguments for your diagnosis:
Browse all condition guides →
Guides by Location
Insurance regulations, deadlines, and escalation pathways differ dramatically by country. Find country-specific guidance:
Browse all country guides →