How do I write an appeal letter for an insurance denial?

Identify the claim precisely (patient, member ID, claim number, date of service), name the denial code you are appealing, make the argument that answers that specific code (proof of timely submission for a filing denial, clinical documentation for a medical-necessity denial, the authorization number for an authorization denial), list your enclosures, and request reconsideration in writing. The strongest letters argue against the code's actual reason, not against the denial in general.

Is this appeal letter generator really free?

Yes, with no account and no card. It also runs entirely in your browser: the letter is assembled on this page from templates, and nothing you type is transmitted or stored anywhere.

Which denials are worth appealing?

Denials where a written appeal changes the outcome: missing authorization (CO-197), timely filing with proof of submission (CO-29), medical necessity (CO-50), experimental or investigational classification (CO-55), network-status errors (PR-242), benefit counts that are simply wrong (PR-119), and documentation requests that were answered (CO-226). Some codes should not be appealed at all: CO-45 contractual write-offs and CO-253 sequestration are the contract and the law working as written, and our denial-code pages say so rather than selling you an appeal.

Free tool

Insurance denial appeal letter generator

Pick the denial code, fill in the claim, and get a professional appeal letter that opens with the argument that actually wins that code's appeals: proof of submission for timely filing, the authorization record for CO-197, the clinical case for medical necessity. Copy it, finish the bracketed specifics, send it. No signup, no card, no email.

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Everything you type stays in your browser. The letter is assembled on this page (no server, no AI call, no storage), which is exactly how a tool that handles patient and claim details should work.

Common questions

How do I write an appeal letter for an insurance denial?: Identify the claim precisely (patient, member ID, claim number, date of service), name the denial code you are appealing, make the argument that answers that specific code (proof of timely submission for a filing denial, clinical documentation for a medical-necessity denial, the authorization number for an authorization denial), list your enclosures, and request reconsideration in writing. The strongest letters argue against the code's actual reason, not against the denial in general.
Is this appeal letter generator really free?: Yes, with no account and no card. It also runs entirely in your browser: the letter is assembled on this page from templates, and nothing you type is transmitted or stored anywhere.
Which denials are worth appealing?: Denials where a written appeal changes the outcome: missing authorization (CO-197), timely filing with proof of submission (CO-29), medical necessity (CO-50), experimental or investigational classification (CO-55), network-status errors (PR-242), benefit counts that are simply wrong (PR-119), and documentation requests that were answered (CO-226). Some codes should not be appealed at all: CO-45 contractual write-offs and CO-253 sequestration are the contract and the law working as written, and our denial-code pages say so rather than selling you an appeal.

Appeal less by denying less

An appeal letter is the expensive way to get paid: it recovers one claim, weeks late. The cheap way is to catch the cause before submission. Our free claim scrubber flags the diagnosis-coding errors behind the most common denials, each denial code page explains how to stop that code recurring, and the paid workspace runs those checks on every claim.

The denials people appeal most

Ranked by how often each code is searched. Every page below names the argument that wins that particular appeal, and says plainly when a code is not worth appealing.

PR-96: Non-covered charge, and the patient owes it. Same reason as CO-96 (the service is not a benefit), but the PR prefix moves the money: instead of a write-off, the payer is saying this amount is legitimately billable to the patient.
PR-204: The service is not covered under the patient's current benefit plan, and the balance is the patient's. Close cousin of PR-96, with one trap worth knowing: 'not covered under THIS plan' sometimes means covered under a different one the patient also has.
CO-197: No prior authorization. The payer required precertification for this service and cannot find one: either it was never obtained, or it was obtained and the claim doesn't show it. Among the most expensive denials there is, and one of the most appealable.
CO-50: The payer does not consider the service medically necessary for the diagnosis you submitted. In Medicare, this almost always means the diagnosis is not on the covered list in the applicable coverage policy for your jurisdiction.
CO-226: The payer asked the billing provider for information and considers the answer missing, incomplete, or late. Somewhere there is a development letter with your name on it: the entire game is finding it and answering it properly.
PR-119: The benefit maximum has been reached: the plan's allowance for this service, this period, is used up, and further charges belong to the patient. The useful question is always: used up according to whom, and is their count right?
PR-242: The services weren't provided by a network or primary-care provider, so the plan is paying less or nothing and assigning the difference to the patient. Before anyone bills the patient, one question matters most: are you actually out of network, or do the payer's records just say so?
CO-131: A claim-specific negotiated discount was applied: a rate agreed for this claim rather than by your standing contract. Fine when you actually negotiated one. The reason to read this page: sometimes you didn't, and the discount is riding on an agreement you never signed.

All 44 denial codes explained