How to appeal an insurance denial

First, check what you are holding

An explanation of benefits is not a bill. It is your insurer's account of what it was charged, what it allowed, what it paid and what it expects you to owe. It usually says this is not a bill somewhere on it, in small type.

A denial arrives on an explanation of benefits, and the provider's bill follows separately. That gap is useful: it means you can often start the appeal before the bill lands, and before anyone is chasing you for money.

Find the reason before you argue with it

Every denial carries a reason code and usually a short remark code beside it. The codes are terse to the point of uselessness, so telephone the number on your insurance card and ask two questions in plain language:

• Why exactly was this denied? Ask for it in writing.
• What criteria were applied? If the answer is that the service was not medically necessary, ask for the clinical policy or coverage criteria the reviewer used, and ask whether a clinician reviewed it.

Write down the date, the time, the name of the person you spoke to and a reference number for the call. You will need that record more than once.

The denials that are not really denials

A large number of denials never reach a question of medical judgement at all. They are data problems, and they are fixed by the billing office rather than by an appeal:

• A coding error — the wrong procedure or diagnosis code, or a missing modifier.
• Missing prior authorisation — sometimes obtainable retrospectively, particularly where the care was urgent.
• Coordination of benefits — the insurer thinks another plan is primary and is waiting for you to confirm which is which.
• Eligibility and dates — the claim was filed against a policy that had ended, or before a new one began.
• Network status — an in-network provider processed as out-of-network, often because the claim went to the wrong entity.

If the reason falls into this group, call the provider's billing office first and ask them to correct and resubmit. That is faster than a formal appeal and does not consume one of your appeal levels.

The internal appeal

If the denial is a genuine coverage decision, the first formal step is an internal appeal — you asking the plan to reconsider. The denial letter must tell you how to file and by when. Many plans allow around six months from the denial, but the letter governs, and a missed deadline is the most common way a good appeal fails.

1. Put it in writing, even if the plan accepts appeals by telephone. Include the member ID, claim number, date of service and provider.
2. State what you want in the first sentence: that the claim be reprocessed and paid.
3. Answer the stated reason directly. If the denial says the service was not medically necessary, the appeal has to explain why it was — not why the bill is unaffordable, which is a different problem with a different remedy.
4. Attach the evidence. Clinic notes, imaging reports, the referral, the prior authorisation number if one exists, and a letter from the treating clinician.
5. Send it so you can prove it arrived and keep a copy of everything.

Get the clinician involved

The two most effective things in a medical-necessity appeal usually come from the doctor's office rather than from you. A letter of medical necessity sets out the diagnosis, what was tried before, and why this treatment was indicated. A peer-to-peer review puts your clinician on the telephone with the plan's medical director.

Ask the practice directly whether they will do both. Many have staff who do nothing else, and the request is routine.

External review

If the internal appeal fails, most plans must then offer an independent external review by a reviewer who does not work for the insurer. This is the part people most often do not know exists, and it is the point at which the decision leaves the company that made it.

Where the request goes depends on the type of plan — for many plans it is your state insurance regulator, and for self-funded employer plans it is a federal process. Your final internal denial letter is required to tell you which route applies and how long you have. Medicare, Medicaid and Veterans Affairs coverage each run their own separate appeal systems.

Where a delay would seriously endanger health, ask for the appeal to be expedited. That request should be handled in a much shorter timeframe, and you can generally run an expedited external review alongside the internal one rather than after it.

What to do about the bill in the meantime

Tell the provider's billing office, in writing, that the claim is under appeal and ask them to place the account on hold. Most will, because an account in dispute is not worth sending to collections. Ask them to confirm the hold in writing and note the date it expires.

At the same time, ask about financial assistance. The two run in parallel and do not conflict: an appeal decides whether the insurer pays, and assistance decides what you owe if it does not. Applying for one does not weaken the other.

If the appeal is finally refused

You still have the ordinary levers. Ask for the itemised bill and check it. Apply for financial assistance if you have not. Ask what the self-pay rate would have been. If the care was emergency care, or was given by an out-of-network clinician at an in-network facility, check whether the No Surprises Act limits what you can be charged regardless of the coverage decision.

And keep the file. Appeals are frequently decided on paperwork rather than on principle, and the person who kept dates, names and copies is in a materially better position than the person who did not.