The first thing to know about appealing a denied claim is that most denials that get appealed win, and most denials never get appealed. That gap is where practices lose recoverable revenue. A denial is not a final answer; it’s the start of a defined process with deadlines, levels, and a required format, and the practices that treat it that way collect money the practices that shrug it off leave on the table.
The second thing to know is that not every denial should be appealed. Some should be fixed and resubmitted as a corrected claim, which is faster and simpler. Knowing which response a denial calls for, appeal or correction, is the difference between getting paid in three weeks and wasting a month on the wrong process. This post covers how to tell them apart, the appeal deadlines that actually matter, the steps for commercial and Medicare appeals, and what goes in an appeal letter that wins.
Appeal or Corrected Claim? Know the Difference First
Before you appeal anything, determine whether the denial actually calls for an appeal or a corrected claim, because they are different processes with different outcomes. Getting this wrong wastes time on both ends.
A corrected claim fixes an error on your end and resubmits the claim for normal processing. Use it when the denial is a data or coding problem: a missing modifier, a wrong diagnosis code, a transposed member ID, a missing NDC. You’re not disputing the payer’s decision; you’re fixing the claim so it can adjudicate correctly. This is faster than an appeal and is the right response to most administrative denials.
An appeal formally challenges the payer’s determination and triggers a defined review process. Use it when you believe the payer decided wrong: a medical-necessity denial where the documentation supports the service, a prior-authorization denial where authorization existed, a timely-filing denial where you have proof of on-time submission, or an underpayment against your contracted rate. You’re not fixing anything; you’re arguing the claim should have been paid as submitted.
The quick test: if the problem is on your claim, correct it. If the problem is the payer’s decision, appeal it. Matching the denial to the right response starts with reading the denial correctly, which means reading the group code, the CARC, and the RARC together, the same discipline covered in our guide to the common denial codes and how to fix each.
The Deadlines That Actually Matter
Appeal deadlines are jurisdictional, which means missing one doesn’t delay your appeal, it ends it, regardless of how strong your case is. The single most important habit in appeals is calendaring the filing deadline the moment a denial posts. Here are the windows that govern most claims:
| Payer | First-level appeal deadline | Notes |
|---|---|---|
| Medicare (Original) | 120 days from the initial determination | Five formal levels; deadlines tighten after Level 1 |
| Commercial (Aetna, Cigna, UHC, BCBS) | Typically 60 to 180 days from the denial | Always confirm the exact window on the denial notice |
| Medicaid | Varies by state and MCO, often 60 to 120 days | Check the specific state and plan |
Two things about this table. First, the commercial range is wide because every payer sets its own window, so the deadline printed on the denial notice is the one that governs, not the range. Second, these are first-level deadlines; each subsequent level has its own, usually shorter, clock. Treat every window as a hard cutoff, not a guideline.
The reason deadlines matter so much is that a missed appeal window is one of the few billing losses with no recovery path. A denied claim can be appealed; an appeal filed late usually cannot be revived. That permanence is why the practices that recover the most denied revenue are the ones with a calendaring discipline, not the ones with the best appeal letters.
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Get My Free Revenue Audit →How to Appeal a Commercial Claim
Commercial appeals follow a two-level structure at most payers: an internal appeal, then an external review. The process is more navigable than Medicare’s five levels, but the deadlines are less standardized, so verification matters more.
Level 1: Internal appeal. You submit a written appeal to the payer, and the payer reviews its own decision. This is where the large majority of appealable denials are won, so it deserves your best documentation the first time. Include the denial reason (the exact CARC/RARC), a clear argument for why the service should be paid, and all supporting documentation. File within the window on the denial notice, typically 60 to 180 days.
Level 2: External review. If the internal appeal fails and the denial involves medical necessity or a coverage determination, you can often request an independent external review, where a reviewer with no relationship to the payer decides. Under the Affordable Care Act’s external review provisions, this independent decision is binding on the plan. Deadlines for requesting external review are set by the plan and state, so confirm them on the internal-appeal denial.
The practical key to commercial appeals is front-loading. Build the strongest possible case at Level 1, because the internal appeal is where most wins happen and because a weak first appeal makes the external review harder. When we work a commercial appeal, the ones that overturn fastest are the ones where the medical-necessity argument and the documentation were complete on the first submission, not added later.
How to Appeal a Medicare Claim
Original Medicare has a five-level appeal structure, and the first two levels resolve the vast majority of cases. Each level has its own reviewer, deadline, and, at higher levels, a minimum dollar threshold. The full structure, per CMS’s Original Medicare appeals process:
Level 1: Redetermination by your Medicare Administrative Contractor (MAC). File within 120 days of the initial determination; the MAC decides within about 60 days.
Level 2: Reconsideration by a Qualified Independent Contractor (QIC), an entity independent of the MAC. File within 180 days of the redetermination decision; the QIC decides within about 60 days.
Level 3: Hearing before an Administrative Law Judge at the Office of Medicare Hearings and Appeals (OMHA). File within 60 days of the Level 2 decision. For 2026, the amount in controversy must be at least $200.
Level 4: Medicare Appeals Council review. File within 60 days of the Level 3 decision.
Level 5: Judicial review in federal district court. File within 60 days of the Level 4 decision. For 2026, the amount in controversy must be at least $1,960.
The practical takeaway is that Levels 1 and 2 are where you fight. Build a complete clinical record at redetermination, the physician letter, diagnostic results, and the relevant NCD or LCD citation, because introducing new evidence later faces restrictions, and few appeals justify the time and dollar thresholds of Levels 3 through 5.
What Goes in a Winning Appeal Letter
A winning appeal letter is short, specific, and tied directly to the denial reason. Payers process large volumes of appeals, so a letter that makes the reviewer hunt for your argument works against you. Every appeal letter should contain:
- Patient and claim identifiers: name, member ID, claim number, date of service.
- The exact denial reason: quote the CARC/RARC from the remittance, so there’s no ambiguity about what you’re contesting.
- A clear, specific argument: why the service should be paid, stated plainly in a sentence or two, not buried in narrative.
- Supporting documentation: medical records, the authorization number if one existed, the contracted rate if you’re disputing an underpayment, and the payer’s own policy language if it supports you.
- A specific request: ask the payer to reprocess and pay the claim, explicitly.
Match the argument to the denial type. A medical-necessity denial needs clinical notes and the diagnosis-to-procedure linkage. A prior-authorization denial needs proof the authorization existed, or a retro-authorization request with clinical justification. A timely-filing denial needs proof of the original on-time submission (the clearinghouse acknowledgment or claim confirmation). The letter’s job is to hand the reviewer exactly what they need to overturn the denial, with nothing to dig for.
Build a Process, Not One-Off Appeals
The practices that recover denied revenue consistently don’t write better one-off appeals; they run a process. That means calendaring every appeal deadline the moment a denial posts, templating appeal letters by denial type and payer so filing is fast, working appeals within days rather than weeks, and tracking win rates by payer and denial reason so you know which denials are worth appealing and which to correct or write off. Appeals are one stage of the broader denial management process that recovers revenue, and a strong appeal workflow only works when it sits on top of a system that catches and categorizes denials in the first place.
The alternative, appealing when someone has time, is how recoverable denials age past their windows and become permanent write-offs. The revenue is winnable; the constraint is process.
Frequently Asked Questions
A corrected claim fixes an error on your end, a missing modifier, a wrong code, a data mistake, and resubmits the claim for normal processing. An appeal formally challenges the payer’s decision on a denied or underpaid claim and triggers a defined review. Use a corrected claim for your own errors and an appeal to dispute the payer’s determination. Choosing the wrong one wastes time.
It depends on the payer. Original Medicare allows 120 days from the initial determination for a first-level redetermination. Commercial payers typically allow 60 to 180 days from the denial, and Medicaid varies by state and plan, often 60 to 120 days. Always confirm the exact deadline on the denial notice, because a missed appeal window usually ends the appeal permanently.
Original Medicare has five levels: redetermination by the MAC, reconsideration by a Qualified Independent Contractor, a hearing before an Administrative Law Judge at OMHA, review by the Medicare Appeals Council, and judicial review in federal court. Levels 3 through 5 have minimum dollar thresholds ($200 at Level 3 and $1,960 at Level 5 for 2026). Most appeals resolve at Level 1 or 2.
An appeal letter should include patient and claim identifiers, the exact denial reason quoted from the CARC/RARC, a clear argument for why the service should be paid, supporting documentation (records, authorization, contracted rate, or policy language), and a specific request to reprocess and pay the claim. Keep it short and tied directly to the denial reason; match the documentation to the denial type.
Yes, if you have proof the claim was originally submitted within the payer’s filing window. Acceptable proof includes the clearinghouse acknowledgment, the original claim confirmation, or a certified mail receipt. Most payers overturn a timely-filing denial when shown the claim was filed on time originally, so these are worth appealing rather than writing off, provided the appeal itself is filed within its own deadline.
Stop Letting Winnable Appeals Expire
Most appealable denials win, and most are never filed, because appeals lose to more urgent work and age past their deadlines. A defined appeal process, right response to each denial, deadlines calendared, letters templated, appeals worked fast, turns denied claims back into paid ones instead of write-offs.
MedBillingTech runs full-cycle medical billing for independent practices at 3.99% of collections, including denial and appeal management that files the right response to each denial, on time, with the documentation that overturns it. No long-term lock-in, and a 97% client retention rate. Mark Wood, our COO, has spent more than 20 years in revenue cycle operations.
If you want to know how much winnable revenue is sitting in your denied and expired claims, our free revenue audit reviews your denials, appeal win rate, and where recoverable money is aging out. Or call (307) 243-2190 to talk through your denials.
