What to Do if Insurance Denies a Claim
A denial letter is not the end. Many appeals succeed, yet very few patients file one. Here is exactly what to do, from someone who processed claims from the inside.
Most plans allow 30 to 180 days to file an internal appeal, and ACA-compliant plans must allow at least 180. Missing the deadline can forfeit your right to appeal, even if the denial is wrong. Find your deadline and put it in your calendar first.
Here is what to do right now — in order
Why bother? Research on ACA marketplace plans (KFF, CMS) shows only a tiny share of denied claims are ever appealed, and a large share of appeals and external reviews succeed. Add exact figures and links before publishing.
The 6 Most Common Reasons Insurance Denies Claims
The denial letter must state the reason. Find your type below; each needs a different appeal strategy.
Medical necessity denial
The insurer says the treatment was not medically necessary. Very winnable on appeal with strong physician documentation.
Prior authorization not obtained
Advance approval was required but not obtained. Often an administrative failure by the provider, not a true coverage issue.
Out-of-network provider
You were treated outside your network, sometimes unknowingly, such as an out-of-network specialist at an in-network hospital.
Experimental or investigational
The insurer labels a treatment experimental even when it is accepted practice, sometimes for newer treatments with strong evidence.
Coverage exclusion
The insurer says your plan excludes the service. Exclusions are often written narrowly, so read the exact language.
Billing or administrative error
A wrong code or incorrect patient information caused the claim to be processed incorrectly. Often the easiest to fix.
What to Do — Step by Step
Follow these in order. The most important thing is to act quickly: your deadline counts down from the date on the denial letter.
Get everything in writing immediately
If you got a verbal denial, call back and request the written denial letter and your Explanation of Benefits (EOB). The letter must include the specific reason, the criteria or policy provision used, and how to appeal.
If any of that is missing, call your insurer and request a more detailed written explanation before doing anything else.
Find your appeal deadline and protect it
Write it down, put it in your calendar, and set a reminder 14 days before. Missing it can permanently end your right to appeal.
Request the clinical criteria used to deny your claim
You have the right to request, in writing, the guidelines your insurer used. Call member services and use the phone script below.
Give those criteria to your doctor. A letter that rebuts the insurer's specific criteria is far more effective than a general statement of necessity.
Get a Letter of Medical Necessity from your doctor
Ask for a detailed letter explaining why the treatment is necessary for your condition, which alternatives were considered and why they fall short, the consequences of going without, and a direct response to the criteria your insurer cited.
File your written internal appeal
Every plan must have an internal appeals process. File in writing, not just by phone, and send by certified mail for proof of date and delivery.
State the claim number and what you are appealing, explain why the denial is wrong, reference your doctor's letter, include supporting records, and request a response within the required timeframe.
If the internal appeal fails — request an Independent External Review
Under the Affordable Care Act, an independent organization separate from your insurer can review your case and issue a binding decision. It is free to you.
The request window is usually 4 months after the final internal denial, so check your final denial letter for the exact date. A substantial share of external reviews, roughly 4 in 10 in published figures, overturn the insurer.
Escalate further if needed
State Insurance Commissioner: files a free complaint and can apply regulatory pressure, sometimes leading to a reversal.
Employer HR: for employer plans, HR often has leverage with the insurer that individual members lack.
Patient advocate or healthcare attorney: for large denials, many work on contingency, so you pay only if you win.
CFPB: if the denied claim has gone to collections, you can file a complaint with the Consumer Financial Protection Bureau.
A Script for Calling Your Insurer
Use this script from Step 3. Read it almost word for word if that helps.
Understanding and disputing a denial
The Full Appeals Escalation Path
Think of it as a ladder: move up only if the step below fails. Most denials are resolved at Step 1 or 2.
Use These Tools Right Now
Insurance Denial Appeal Builder
A personalized appeal letter for your denial type in under 3 minutes. Includes a deadline calculator, 6 denial types, and formal and email versions.
Free Insurance Appeal Checklist
The 20-item filing checklist with a denial reason decoder, deadline tracker and documents guide. Works right in your browser.
Hospital Financial Assistance Guide
If your appeal fails, assistance programs exist. Nonprofit hospitals in the U.S. are required to offer them.
✓ Immediate action checklist — do these today
Your first step depends on which plan denied you
The framework above still applies: read the denial notice, note the deadline, gather documentation and use the phone script. Who you contact next differs.
Private or workplace plan: call your plan administrator or insurer and follow their internal appeals process. If it is not resolved, the OmbudService for Life & Health Insurance (OLHI) handles unresolved complaints about many private insurers. In Quebec, the Autorité des marchés financiers (AMF) is the regulator to contact.
Provincial program: if a provincial plan denied a specific approval or an out-of-province claim, appeals go through that province's own review process, such as a review by the plan and then an independent tribunal or appeal board. Steps and time limits vary by province and territory, so check your denial notice.
Understand your denial letter firstCommon Questions About Denials
Do I need a lawyer to appeal a denial?
Generally not for a standard internal appeal — many patients handle this themselves with good documentation. Complex or high-value cases are where legal help is more commonly considered.
What if I miss the appeal deadline?
Contact your insurer immediately — some may grant an extension for good cause, but this isn't guaranteed, which is why acting early matters.
Can my doctor help with the appeal?
Often yes — a Letter of Medical Necessity from your provider that directly addresses the insurer's stated reason is frequently the most persuasive piece of an appeal.
How long does an appeal take?
Timeframes vary by insurer and urgency — standard internal appeals must get a response within 30 days, urgent appeals within 72 hours. Ask your insurer directly what to expect for your case.
This guide is general information, not legal or medical advice. Rules differ by plan and state or province; follow the instructions in your own denial letter.