A denial letter is written to sound like a final answer. It is not one. It is the insurance company's first answer, and there are formal steps after it, real deadlines, and one stage where somebody outside the insurance company decides. Most people never use any of it. Insurers denied about one in five in-network claims on HealthCare.gov plans in 2024, and fewer than one percent of those denials were appealed. So start where an agent would start. Read it. Work out what kind of denial it is. Then aim at the right target.
Step one: find out why, precisely
The reason is on the letter, usually behind a code. Find it before you do anything else.
Somewhere in the denial letter and your Explanation of Benefits (the summary your plan sends showing what it paid and what it did not) is a reason, usually behind a code. There are five common kinds. The fix depends entirely on which one you got.
The five common kinds of denial, and what fixes each one
| What the letter says | What to do about it |
|---|---|
| Administrative or coding error | A paperwork mistake: wrong code, wrong ID, billed twice. Call the billing office and ask them to correct and resubmit. |
| Not medically necessary | The plan is disagreeing with your doctor. Ask your doctor's office for a letter of medical necessity. This one is theirs to fight. |
| No prior authorization | The care needed approval in advance and nobody got it. Often still fixable, especially for urgent care. Ask the provider to request it retroactively. |
| Out of network | The provider is not on your plan's list. Harder, but emergencies are protected. See the note on surprise billing below. |
| Not a covered benefit | The plan says it does not cover this at all. Read the plan documents yourself, because plans are sometimes wrong about their own terms. |
Scroll the table sideways to see every column.
Administrative errors are the largest named category in federal data, about 25% of denials in 2024, and the easiest to reverse.
Two things you are entitled to ask for in writing, at no charge: the denial code and what it means, and the specific plan rule or clinical standard used to deny you. If the denial turned on medical judgment, you can also ask for the clinical rationale. Plans have to provide these, and appeals get much easier once you have them.
One more check before you fight anything. Look at the patient responsibility line on your Explanation of Benefits. If an in-network claim was denied because the provider missed a prior authorization or filed late, that is often the provider's problem under their contract, not yours, and the bill you received may simply be wrong.
Step two: call, and take notes
One phone call fixes a lot of these. Write down who you talked to.
Call the number on the denial letter and ask three questions.
Write down the date, the representative's name, and the reference number for the call. You will want all three later.
Then call your provider's billing office. They fight denials for a living and the money is theirs too. A lot of coding errors get fixed right here, with no formal appeal at all.
- What is the reason, in plain language?
- What exactly would change the outcome?
- How do I file an appeal, and by when?
Step three: file the internal appeal, on time
You usually get 180 days. The file matters more than the letter.
Most plans have to offer an internal appeal, and your denial letter has to tell you how to file and by when. For most plans you get 180 days, which is six months, from the date of the denial notice. That sounds like plenty. It is not, once you are waiting on your doctor's office. Start now.
The clocks that matter, and who is on them
| Step | Deadline |
|---|---|
| You file the internal appeal | 180 days from the denial notice |
| Plan decides, care not yet received | 30 days |
| Plan decides, care already received | 60 days |
| Plan decides, urgent case | 72 hours |
| You request external review | 4 months from the final internal denial |
| Outside reviewer decides | 45 days, or 72 hours if urgent |
Scroll the table sideways to see every column.
These are the federal floors for ACA-compliant plans. Your plan can give you longer but not shorter, and the dates in your own letter control. Short-term plans are not ACA plans and do not carry these rights.
Your appeal file needs four things. A short cover letter: what was denied, why that is wrong, what you want. The denial letter and any Explanation of Benefits forms. A letter of medical necessity from your doctor, which matters more than anything else you can send. And any records or clinical guidelines your doctor points to.
Keep copies. Send it trackable.
Step four: escalate to independent review
This is the one stage where the insurer is not grading its own work.
Lost the internal appeal? You can usually ask for an external review. Someone outside the insurance company reads your file and decides, and by law the insurer has to accept that decision. You get 4 months from the final internal denial to ask.
Up to this point, the company that said no is the company reviewing whether no was right. External review ends that. It is built for one particular fight: the plan said no on medical grounds and your doctor disagrees. If that is the denial you are holding, this is the stage that matters most.
Insurers upheld about two thirds of internal appeals in 2024. That is the stage where the plan is reviewing itself. External review is different in kind, not just in odds: the decision is made by someone with no stake in it, and the plan is bound by the result. Almost nobody gets there. Only about 4% of upheld appeals went on to external review. Most people stop at the first no. Do not.
Step five: who else can help
Three places will help you for free, and your denial notice has to name one of them.
Which regulator can help depends on who actually pays your claims. If you bought your own plan, or your employer coverage is fully insured, your state department of insurance takes complaints and can apply pressure on conduct and timelines. If your employer self-funds the plan, which is common at larger companies, the state has no authority over it. That call goes to the US Department of Labor at 1-866-444-3272. Your HR or benefits team can tell you which kind you have in one question.
Most states also run a free Consumer Assistance Program that will help you prepare and file the appeal itself. If your state has one, your denial notice has to name it. That is the closest thing to having someone in your corner at no cost, and it is the most underused resource on this page.
For the external review stage, the notice you receive also has to give you the contact information for the independent organization that will handle it. If your plan does not participate in a state or federal external review process, it has to contract with an independent review organization on its own. Either way you are not expected to find the reviewer yourself.
Your doctor's office is the other resource people forget. Billing staff deal with denials daily, and they can often tell you in one call whether the problem is the code or the coverage.
Between the Consumer Assistance Program, your state department of insurance or the Department of Labor, and your doctor's billing office, most people have more support available than they realize. None of it costs anything.
Preventing the next one
Two minutes of paperwork now prevents the next fight.
Get prior authorizations confirmed in writing before any scheduled procedure.
Check the network status of everyone involved. The hospital, the surgeon and the anesthesiologist can each be a different answer, and that is how surprise bills happen.
And whenever someone at the plan tells you something is covered, ask for the call's reference number. Two extra minutes now can save you a bill later.