How to Appeal a Denied Claim
A denial is not the end of a claim — it is the start of a process with rules, deadlines and a paper trail. This guide walks through that process in order: how to read the denial, what to fix and resubmit, what belongs in a strong appeal letter, and how the Medicare and commercial appeal ladders actually work.
A denied claim is a decision, not a dead end — but overturning it is a disciplined process, not a phone call and a hope. Every denial arrives with a reason code, a deadline and a specific route for challenging it. Practices that recover denied revenue consistently do three things well: they read the denial precisely before acting, they separate simple corrections from true appeals, and they work every appeal against the payer's clock instead of their own. Here is the process, step by step.
Step 1: Read the denial before you touch the claim
The remittance advice — the paper EOB or the electronic 835 — tells you exactly why the claim failed, in two code sets. The CARC (Claim Adjustment Reason Code) states the payer's reason: CO-50 for a service deemed not medically necessary, CO-97 when a procedure is bundled into another payment, CO-16 when the claim lacks information, CO-4 when a modifier is missing or inconsistent. The RARC (Remittance Advice Remark Code) adds the detail the CARC leaves out — which modifier, which document, which eligibility segment failed.
Read both codes together, then read the actual claim next to them. A large share of "appeals" are lost before they start because staff respond to the denial they expected instead of the one on the page. Our denial codes explained guide decodes the codes practices see most, with the fix each one usually calls for.
Step 2: Separate corrected claims from true appeals
Not every denial needs an appeal, and sending a formal appeal for a fixable error wastes the one resource you cannot recover: time inside the filing window.
- Correct and resubmit when the denial is a claim defect: a typo in the member ID, a missing or wrong modifier, an incorrect place of service, a coding mismatch between diagnosis and procedure. Fix the field, submit a corrected claim (frequency/type-of-bill indicators where the payer requires them), and note the original claim number so the payer links the two instead of denying the second as a duplicate.
- Appeal when the claim was billed correctly and you dispute the payer's judgment: medical-necessity denials, bundling decisions you believe misread the documentation, downcoding, timely-filing denials where you hold proof of submission, and contract-interpretation disputes.
- Write off or bill the patient only where the denial and the contract genuinely allow it — a non-covered service with a valid advance notice, for example. Some denials are contractual adjustments the practice must absorb; chasing those burns the same hours a winnable appeal needed.
Step 3: Gather the documentation before you write a word
Appeals are decided on paper, by a reviewer comparing your file against the payer's policy. Assemble the evidence first: the clinical notes for the date of service, with the elements that establish medical necessity highlighted; relevant test results, imaging or operative reports; the authorization record if the service required one; proof of timely filing (clearinghouse acceptance reports, not just your submission log) for filing-limit disputes; and the payer policy, LCD or contract clause that supports your position, cited by name or number where you can find it.
If the documentation genuinely does not support the service, stop. A weak appeal teaches the payer nothing and spends staff time; the honest fix is a documentation conversation with the provider and a corrected workflow, not a louder letter.
Step 4: Write an appeal letter that makes 'yes' easy
A strong appeal letter is short, specific and organized the way a reviewer works. It contains:
- Identification up top: patient name and member ID, date of service, claim number, provider NPI and tax ID, and the exact denial code being appealed.
- One clear ask: state in the first lines that you are requesting reconsideration and reprocessing of the claim, and why the denial is incorrect under the payer's own policy.
- The case, in the reviewer's order: what was done, why it was medically necessary or contractually payable, and which attached document proves each point — referenced by page or exhibit, not buried in a stack.
- A specific closing: the action requested (reprocess at the contracted rate, overturn the bundling edit), a contact name and number, and a list of attachments.
Send it through the channel the payer specifies — portal, fax or mail — and keep the transmission confirmation. An appeal you cannot prove was received is an appeal the payer can say never arrived. This is the daily work of our denial management and appeals service: every appeal logged, evidenced and tracked to a decision.
Medicare appeals: the five-level ladder
Medicare fee-for-service appeals climb a defined ladder, and each level has its own filing window and decision-maker:
- Level 1 — Redetermination by the Medicare Administrative Contractor (MAC). The request must be filed within 120 days from the date of the initial determination (the remittance notice date). This is a fresh review by staff not involved in the original decision.
- Level 2 — Reconsideration by a Qualified Independent Contractor (QIC), generally within 180 days of the redetermination decision.
- Level 3 — Hearing before an Administrative Law Judge at the Office of Medicare Hearings and Appeals (OMJ), subject to an amount-in-controversy threshold that is adjusted annually.
- Level 4 — Review by the Medicare Appeals Council.
- Level 5 — Judicial review in federal district court, again subject to an amount-in-controversy threshold.
Most practice-level Medicare denials are won or lost at Levels 1 and 2, on documentation. Miss the 120-day redetermination window and the ladder effectively closes, absent a good-cause exception — which is why denial queues are worked newest-deadline-first, not oldest-claim-first.
Commercial payer appeals: every contract writes its own rules
Commercial payers have no single ladder. Appeal levels, forms, submission channels and — most importantly — deadlines are set by each plan and each provider contract, and they vary widely: one payer may allow 180 days from the denial, another 90, an ERISA plan another window again. Some require a first-level appeal before any peer-to-peer or second level is available; some route everything through a portal with no paper option.
The operational answer is a payer matrix: for each major payer, the appeal address or portal, the deadline, the required form, and whether corrected claims and appeals travel the same route. Build it once, keep it current, and no appeal should ever die because a biller used the wrong payer's rules. Where a specific dollar threshold or state prompt-pay law helps escalate, your contract and state regulations — not general advice — govern.
Track every appeal like money, because it is
An appeal log is not bureaucracy; it is the difference between a process and a pile. Log the claim, denial code, appeal date, channel, proof of submission, follow-up date and outcome for every appeal. Work the log on a cadence: confirm receipt within days, check status before the payer's stated decision window expires, and escalate — second level, peer-to-peer, supervisor review, or state insurance department complaint where appropriate — the moment a payer misses its own timeline. Aging appeals belong on the same worklist discipline as aging claims in your accounts receivable management: untouched inventory loses value every week.
When the same denial keeps coming back
Appeals recover revenue; they do not fix causes. If the same denial code lands every week — the same modifier edit, the same authorization gap, the same documentation shortfall — the practice does not have an appeal problem, it has a front-end problem, and every week spent appealing is a week the defect bills again. Trend your denials by code, payer and provider, fix the top cause at the source, and let the appeal volume fall. Our guide on how to reduce claim denials covers the prevention side: the eligibility, authorization and coding checks that stop the most common denials from being created at all.
Frequently asked questions
How long do I have to appeal a denied Medicare claim?
For Medicare fee-for-service, the first level — a redetermination by your Medicare Administrative Contractor — must be requested within 120 days of the date on the initial determination notice (usually the remittance advice). Later levels have their own windows, generally 180 days from the prior decision. Missing the first deadline closes the ladder in most cases, so denied Medicare claims should be worked well before day 120.
What is the difference between a corrected claim and an appeal?
A corrected claim fixes a defect on the original submission — a wrong modifier, a typo in the member ID, a mismatched code — and is resubmitted as a correction. An appeal asks the payer to reverse a judgment made on a claim that was billed correctly, such as a medical-necessity or bundling decision. Sending an appeal for a simple error wastes time, and resubmitting a disputed claim unchanged usually earns a duplicate denial.
How long does a commercial payer appeal take to decide?
It depends on the plan and the contract. Many payers state decision windows in the range of 30 to 60 days for a first-level appeal, but the contract and applicable state law control. What matters operationally is proving timely submission, confirming receipt, and following up before the stated window expires — then escalating to the next level promptly if the payer misses its own deadline or upholds the denial.