A denial letter starts a process, not a verdict. These six common missteps cost people time, money and sometimes the claim itself, and each one is easy to avoid.

This guide is general information, not insurance, tax or legal advice. Rules, limits and deadlines change each year, so check HealthCare.gov, Medicare.gov or your insurer for your situation.

A denial letter from your health insurer can feel like a closed door, but it is really the first step in a process with defined rights and deadlines. Many appeals fail not because the claim was weak, but because of avoidable errors along the way: a missed date, a letter that says nothing new, a paper trail that never existed. Here are six mistakes to watch for, and what to do instead.

Mistake 1: Not Asking Why the Claim Was Denied

An appeal built on guesswork rarely works. Your insurer is required to notify you in writing and explain why it denied a claim, within 30 days for medical services you have already received. For plan years beginning on or after July 1, 2011, that notice must also spell out your right to file an internal appeal and, if that fails, your right to request an external review.

Read the denial letter and the Explanation of Benefits closely. The stated reason tells you what evidence you need. A denial for an out-of-network provider calls for a different response than one claiming the treatment was not medically necessary or was experimental. If the letter is vague, call the insurer and ask for the specific plan provision or medical rationale behind the decision, then get it confirmed in writing.

The reason also matters for what comes later. Denials involving medical judgment, treatments labeled experimental, and cancellations of coverage based on allegedly false application information are the kinds of denials that can go to external review. Knowing the reason up front helps you plan the whole route.

Mistake 2: Missing the Appeal Deadline

Deadlines in the appeals process are firm, and they arrive faster than many people expect. A few of the timeframes set by federal rules and state law:

• Internal appeals for a service you have not yet received must generally be completed within 30 days; appeals for services already received within 60 days.
• In some states, such as Nebraska, you must file your internal appeal within 180 days of receiving the denial notice.
• You must file a written request for external review within 4 months after the date you receive the final denial of your internal appeal.

Urgent situations follow different tracks. If waiting for a standard decision would seriously jeopardize your life, health or ability to regain maximum function, you can request an expedited appeal, and an urgent-care internal appeal must be decided within 72 hours of the insurer receiving the request.

Important: The 4-month external review window runs from the date of the final internal denial. If it passes, you can lose your eligibility for external review entirely, so mark the date as soon as that letter arrives.

If the timeline on your paperwork is unclear, call your state insurance department. Rules vary by state, and the department can tell you which deadlines apply to your plan.

Mistake 3: Resubmitting Without New Information

Sending the same claim back with the same paperwork invites the same answer. An internal appeal is your chance to give the insurer something it did not have the first time: a letter from your doctor explaining why the treatment is medically necessary, additional medical records, or clarification of a coding or network error.

Start by matching your response to the stated denial reason. If the insurer said the service was not medically necessary, a physician’s written justification is the evidence that addresses it. If it said the provider was out of network, gather documents showing the network status or the circumstances of the care. If prior authorization was the issue, our explainer on prior authorization describes why insurers require approval before certain services and how a missing approval can be addressed.

Also confirm what you are appealing. Denials can be appealed when the benefit is not offered under your plan, when the insurer says the problem began before your coverage started, when the provider was out of network, when you are no longer enrolled or eligible, or when the insurer is canceling your coverage based on your application answers. Some of these, such as an alleged application error, involve facts you can correct or contest with documents.

Mistake 4: Going It Alone Instead of Using Your Doctor’s Support

Your treating provider often has the strongest voice in an appeal, especially when the denial turns on medical judgment. Ask your doctor for a letter that addresses the insurer’s stated reason directly, explaining your condition, why the treatment is appropriate, and what happens without it. Relevant medical records attached to that letter strengthen it further.

You do not have to file the appeal yourself, either. You can name a family member, friend, advocate or attorney as your authorized representative to act on your behalf. Many states have Consumer Assistance Programs that can file an appeal for you, and patient advocates can handle medical billing issues on your behalf if you are sick or overwhelmed.

One more source of help depends on where your coverage comes from. If you have insurance through an employer, ask your human resources department whether the plan is self-funded, meaning the employer carries the risk. In self-funded plans, employers can make exceptions in accordance with their plan rules, so a direct request to the employer can be worth a phone call.

Mistake 5: Ignoring External Review as a Next Step

If the internal appeal fails, the process is not over. External review takes your case to an independent third party, and the insurance company is required by law to accept the reviewer’s decision. In other words, the insurer no longer gets the final say over whether to pay.

External review exists for denials involving medical judgment, treatments deemed experimental or investigational, and coverage cancellations based on allegedly false application information. The reviewer either upholds the insurer or decides in your favor, and if the denial is overturned, the insurer must provide the payments or services you requested. The results can be surprisingly favorable: in Massachusetts, for example, the state reports that generally over 40 percent of external review decisions are resolved in favor of the patient.

Details to know before you file:

• The request must be in writing, within 4 months of the final denial.
• A fee of up to $25 may apply, often capped at $75 per plan year, and it is frequently waived for financial hardship or for people covered by programs such as Medicaid.
• Your denial notice or EOB should include contact information for the organization that handles external review in your state.
• If waiting would seriously jeopardize your life or health, you can request an expedited external review, and an urgent internal appeal and external review may be able to proceed at the same time.

Mistake 6: Keeping No Paper Trail of Calls and Letters

Appeals can stretch over months and involve several people at the insurer. Without records, you have no way to prove what you submitted or what you were told. Keep copies of the EOB forms and denial letters, the request for internal appeal you sent, every document you submitted, and any form you signed allowing someone else to file for you.

Take notes during every phone call: the day, the time, the name and title of the person you spoke with, and what was said. If the insurer’s decision letters are confusing, our guide to health insurance terms can help you decode the jargon before you respond.

One practical rule covers everything: send copies, never originals. Your insurer needs the original request for an internal appeal and any authorization form, but supporting documents should go in as copies. Keep your own complete set, and if necessary you can request a copy of your entire claim file from the insurance company at no charge. Also keep paying your premiums and stay enrolled during the appeal, because dropping coverage can force you to wait to re-enroll even if the appeal succeeds.

Before you make the next call, set up a folder, paper or digital, for the denial letter, your appeal form and a running log of every conversation.

If your claim has already been denied, pull out that letter today, note the reason and the deadline, and start your internal appeal while the clock is still on your side.

Frequently asked questions

How long do I have to appeal a denied health claim?
Deadlines depend on your plan and your state. Nebraska, for example, gives you 180 days from the denial notice to file an internal appeal, and external review requests generally must be filed within 4 months of a final denial. Check your denial letter and your state insurance department for the deadline that applies to you.

What is an external review?
External review means an independent third party, often an independent review organization, examines your insurer’s decision. The insurer must accept the reviewer’s decision, so the insurance company no longer gets the final say.

Can someone file the appeal for me?
Yes. You can name a trusted person, such as a family member or attorney, as your authorized representative, and some states have Consumer Assistance Programs that can file an appeal for you. Your doctor can also support the appeal with a letter or records.

Does external review cost money?
Some plans or states charge a fee of up to $25 per external review, often capped at $75 per plan year, and the fee is frequently waived for financial hardship. Check your denial notice or your state insurance department before you file.