The short answer
A denied claim is not a final answer. Read the denial letter for three things: the reason code, the deadline to appeal and the appeal route. Request the itemised bill and check it for duplicate or wrong lines. Then appeal in writing: state the claim, the reason given, why it is wrong, and the evidence that proves it, attached. Keep copies and dates of everything, and send it well before the deadline.
Reading the denial letter
A denial letter, often called an explanation of benefits (EOB) in the US, usually tells you three things, even when it is hard to read:
| What to find | Why it matters |
|---|---|
| The reason code and its wording | It tells you what the insurer says is missing or wrong, and so what evidence the appeal needs |
| The appeal deadline | A late appeal can be refused without being read |
| The appeal route | Where to send it, in what form, and what happens next if it is refused |
Many denials are administrative rather than medical: a missing referral or authorisation, a coding error, a claim sent to the wrong plan. Those can often be fixed with a document you already have.
Checking the itemised bill
The summary bill shows totals. The itemised bill lists every service with its code, date and price, and it usually has to be requested from the provider. Check it line by line for services charged twice, services you did not receive, and dates that do not match your visit. A duplicated line is invisible on the summary and obvious on the itemised version.
How to write the appeal in six steps
1. Note the deadline first
Put it in your calendar with a reminder a week earlier.
2. Decode the reason
Look up the reason code in the letter or on the insurer’s website, or call and ask what it means for this claim. Write down the date, the name of the person and what they said.
3. Gather the evidence
The document that answers the reason: a referral, an authorisation, a corrected code, a letter from the doctor.
4. Check the itemised bill
Any duplicate or wrong line goes in the same letter.
5. Write the appeal
Short and factual: the claim, the reason given, why it is wrong, the evidence attached, and what you are asking for.
6. Send it with a record
Use the route the letter names, keep a copy of everything sent, and note the date.
Worked example: Nia
The scenario
$860 denied, for a reason nobody had read
Nia Carter is 44, works at a desk in Seattle and has two children under ten. $860 of a claim had been denied, and the letter carried a code she did not understand. She had not read the reason.
The reason. The denial carried reason code CO-15, which in Nia’s letter meant the referral was missing or invalid. Her referral existed: it had been issued 17 days before the appointment but had not been included with the submitted claim. That is a clerical failure, and fixable with a document she already had.
The bill. On the itemised bill, which she had to request, line 4 repeated line 2: the same code, the same date and the same $210.
The appeal. One letter, with the referral attached, asked for the $860 to be paid and the $210 duplicate removed, well within the deadline, which was 31 days away. The $860 was approved and the $210 removed: $1,070 in total.
The appeal letter, part by part
What I am asking for. Payment of [amount] denied on [date], and removal of [any duplicate or wrong line, with its amount].
The reason given. Reason code [code]: [the wording on the letter].
Why it is wrong. [The fact that answers the reason, e.g. a referral was issued on (date), before the appointment on (date), and is attached.]
The bill. [Line X repeats line Y: same code, same date, same amount.]
Attached. [Denial letter, itemised bill, referral or authorisation, any letter from the provider.]
Try it: a shortened Prompt 10
This is a shortened version of Prompt 10 from the Health & Fitness pack, set up to run on its own. Paste it into ChatGPT, Claude or Gemini and fill in the brackets.
You are a former medical billing advocate who has helped patients recover denied claims and remove billing errors. A denial is not a final answer: it has a stated reason, a deadline and an appeal route, and a factual written appeal with the evidence attached is the strongest way through it. You work only from the documents provided and never guess a billing code or a policy term. THE DOCUMENTS (remove your name, address and account numbers before pasting): - The denial letter or explanation of benefits: [paste the reason code, wording, amounts and deadline] - The itemised bill: [paste each line: code, date, description, amount] - The relevant part of your policy, if you have it: [paste] - Evidence you hold: [referral, authorisation, letters, with dates] Produce: 1. THE DENIAL DECODED. What the reason means for this claim, the deadline, and the appeal route, in plain words. 2. THE BILL CHECK. Every duplicate, unexpected or mismatched line, with its amount. 3. THE APPEAL LETTER. One page: what is asked for, the reason given, why it is wrong, the bill errors, and the evidence attached. 4. THE NEXT STEPS. What to send, to whom, by when, and what happens if the appeal is refused. Where the documents are unclear, write [CHECK POLICY] or [ASK INSURER] instead of guessing. This is not medical, legal or financial advice.
The full Prompt 10 has eight parts rather than four. In Claude it also builds the appeal as a Word letter, and it reads the Health Brief built by the earlier prompts. The pack gives general information only and never diagnoses or changes a treatment.
If the appeal is refused
Most plans have more than one level of review. In the US, many health plans must offer an internal appeal and then an external review by an independent organisation; your denial letter or plan documents describe the steps and deadlines that apply to you. Your state insurance department can also explain your rights. Rules differ by country, plan and state, so confirm them with your insurer or your plan documents.
Checks before you send
- The appeal will arrive well before the deadline.
- The letter answers the specific reason code.
- The evidence is attached and listed.
- The itemised bill has been checked line by line.
- You have a copy of everything sent, with the date.
Questions
How do I appeal a denied health insurance claim?
Read the denial for the reason, the deadline and the appeal route. Gather the evidence that answers the reason, check the itemised bill, and send a short factual appeal letter with the documents attached, keeping a copy.
What does a denial reason code mean?
It is the insurer’s standard code for why the claim was not paid, such as a missing authorisation or a coding problem. The wording on your letter, or a call to the insurer, tells you what it means for your claim.
How do I get an itemised medical bill?
Ask the provider’s billing office for an itemised statement listing every service with its code, date and charge. Compare it with your explanation of benefits.
Should I paste my medical documents into ChatGPT?
Remove your name, address, member ID and account numbers first, and share only what the question needs. Check the privacy settings of the tool you use.
Written by a former Gartner Managing Partner and investment banking SVP
The guides and the prompt templates on this site come from a career spent building these documents: board decks, forecasts, business cases and hiring decisions, as Managing Partner at Gartner, SVP in investment banking and Country Manager at international subsidiaries. The worked examples are published in full on each product page. Browse the Prompt Library.
Nia Carter, her claim and the insurer are fictional, and the figures are illustrative.
This guide gives general information, not medical, legal or financial advice. Appeal rights differ by country, plan and state; confirm them with your insurer. Output from any AI tool should be reviewed before use.