Your Insurer Denied the Claim. Almost Nobody Appeals, and a Third Who Do Win.

The letter is one page and it is mostly codes. Somewhere in the middle, in the same font as everything else, is the sentence that matters: this claim has been denied. There is a number at the bottom that is now, apparently, yours.

Most people read it twice, feel the specific sinking that comes with an unexpected bill, and file it.

That filing is the expensive part.

One in five claims is denied. Fewer than one in a hundred is appealed.

The numbers are not a secret. Insurers on the federal marketplace have to report them, and KFF publishes the analysis every year.

In the 2024 plan year, HealthCare.gov insurers processed roughly 451 million in-network claims and denied about 85 million of them. That is 19 per cent, close enough to one in five that you can use it as a rule of thumb.

Now the part that makes the first number worth knowing. Of the appeals that were filed, insurers upheld 66 per cent. Which means they reversed about a third.

Read that as a ratio and it is uncomfortable. Roughly one in three people who pushed back got a different answer, and roughly ninety-nine in a hundred never found out what would have happened, because they never asked.

The denial is usually not a doctor disagreeing with you

The intuition most people have about a denied claim is that somewhere in a building an insurance company’s physician looked at their case and decided the treatment was not warranted. That is a specific and slightly humiliating thing to imagine, and it is one reason the letter goes into a drawer.

It is also, in the overwhelming majority of cases, not what happened.

The same reporting that gives us the denial rate gives us the stated reasons. In 2024, across in-network claims:

• 36 per cent were denied for reasons the insurer classified only as “other”
• 25 per cent were administrative
• 13 per cent were service exclusions, meaning the plan does not cover that thing
• 9 per cent were a missing prior authorisation or referral
• 5 per cent were medical necessity

Five per cent. The category everybody imagines is the smallest one on the list, and the largest is a category that does not describe anything at all.

That last point deserves saying plainly, because it limits everything else here. When 36 per cent of denials are filed under “other”, what is actually behind a third of refusals is unclear from the public data, and KFF says as much. So the honest version of the reasons list is: most denials are probably not clinical, a quarter are definitely administrative, and for a large slice nobody outside the insurer can say. That is a reason to ask what your own reason code means rather than to assume you already know.

A quarter of denials are administrative, which is a polite word for a form. A wrong code, a missing referral, a date that does not match, a provider filed under the wrong network status. None of that is a judgement about your health. All of it is fixable, and some of it is fixable with a phone call.

What the law actually gives you, and when

If your plan is not grandfathered, which covers most people with private coverage, the Affordable Care Act gives you two rounds. Both of them run on clocks.

The first is the internal appeal: you ask the insurer to look again. You have 180 days from the denial notice to file it. That is six months, and it is much longer than most people assume, which matters because most people assume there is no window at all.

The insurer then has its own deadline. If you have not had the service yet, they have 30 days. If you have already had it and this is about the bill, they have 60 days. If the situation is urgent, the decision has to come as fast as your condition requires.

The second round is the external review, and it is the one worth understanding properly, because it is the only point in this process where the insurer stops being the judge. An independent organisation reviews the case, and your insurer is required by law to accept the outcome. You have four months after the final internal denial to request one. A standard review is decided within 45 days; an expedited one within 72 hours.

Almost nobody knows any of this

It would be reasonable to assume that people skip the appeal because they have weighed it up and decided it is not worth the trouble. The survey evidence says something simpler and sadder.

KFF’s Survey of Consumer Experiences with Health Insurance, fielded in early 2023, found that 69 per cent of insured adults whose claim had been denied did not know they had the right to appeal it. Eighty-six per cent did not know which government agency to go to for help. Fifteen per cent filed a formal appeal.

Eighteen per cent of insured adults had a claim denied in the previous year. Those who did were about half as likely to say their problem ended up resolved: 29 per cent, against 59 per cent for people whose insurance problem was something else.

The gap between “a third of appeals succeed” and “sixty-nine per cent did not know they could appeal” is the whole subject of this article.

What to actually do with the letter

What follows is a sequence, not a strategy. It is deliberately short, because the thing that stops people is not complexity.

1. Find the reason code, then ask what it means. The denial notice will cite a reason. If it is vague, and a third of them are recorded as “other”, call the number on the letter and ask them to tell you the specific reason and the billing and diagnosis codes on the claim. Since 2011 those codes do not have to be printed on the notice, but they must be made available to you on request. Write down who you spoke to and when.
2. Check the boring things first. Was the provider in network on the date of service? Was a referral or prior authorisation required, and was it obtained? Is the date right? Is the code the one your doctor’s office intended? A quarter of denials are administrative, and this is where they live. Your provider’s billing office deals with this daily and is often the fastest route: a resubmitted claim with a corrected code is not an appeal at all.
3. If it is not a clerical error, file the internal appeal in writing. You have 180 days. Say what was denied, why you think it should be covered, and attach what supports it — the plan document language if the service is covered, a letter from the treating clinician if the question is whether it was needed. Keep it short and specific. Send it so you can prove you sent it.
4. Ask your clinician’s office to write the medical necessity letter. If the denial does turn on necessity, this is the document that carries the case, and it is a routine thing to ask for. It should say what the condition is, what was done, why the alternative was inappropriate, and what happens without it.
5. If the internal appeal fails and the denial was about clinical judgement, request the external review. Four months, independent reviewer, binding on the insurer. The denial letter has to tell you how to start it.
6. If the denial was not about clinical judgement, go sideways instead. Your state insurance regulator takes complaints. So does the federal marketplace. Employer plans have a benefits administrator whose job includes this. These are slower and less certain than external review, and they are not nothing.

The parts of this that are genuinely hard

It would be dishonest to end on a numbered list and imply the process is merely tedious.

It is not evenly hard. Appealing takes phone calls during working hours, letters, and the specific energy required to be politely persistent with an organisation that is not in a hurry. People who are unwell are the population least able to spend that, which is the uncomfortable design flaw at the centre of the whole system: the appeal right is strongest for the people with the most capacity to use it.

The overturn rate should also be read carefully. About a third of appeals succeed, but the people who appeal are not a random sample of the people who were denied: they are likely to be the ones with a stronger case, more time, or a billing office already helping them. It is not safe to assume that a third of all denials would be reversed if everyone appealed. What the number does establish is that pushing back is not futile, which is the belief the low appeal rate suggests most people hold.

The 66 per cent upheld rate is also real. A third of appeals succeeding means two thirds do not, and some denials are correct. The plan genuinely does not cover the thing, and no amount of persistence changes that. Knowing which kind you have is most of the work, which is why step one is asking what the reason actually was.

And this article covers the federal floor for non-grandfathered private plans. Medicare, Medicaid and short-term plans run different processes with different clocks. If that is your coverage, the shape of the argument holds and the deadlines do not. This is an explanation of how the process works rather than advice about your claim: deadlines and rights vary by plan and by state, the ones that bind you are in your own plan documents, and a large or complicated denial is worth taking to someone who does this for a living.

The bottom line

A denial letter reads like a verdict and functions like an opening position. The system’s own numbers say so: about one in five in-network claims is refused, only five per cent of those refusals are about whether the care was needed, and roughly a third of the people who push back get a different answer.

Fewer than one in a hundred pushes back, and the main reason is not resignation. It is that nobody told them the clock had started.

You have 180 days. Start by finding out what the reason code actually says.

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