Medical Claim Denial Management: Deadlines, Appeals, and External Review

If your health insurer refused to pay a claim, you have a right to challenge that decision, and the medical claim denial appeal process is built around a federal 180-day window to file an internal appeal, followed by an independent external review if the insurer still says no.¹ A real share of denials get overturned when people actually push back, but only if the appeal addresses the specific reason the insurer gave and arrives before the deadline runs out.

Start by Decoding the Denial Notice

Every denial comes with an Explanation of Benefits or, for providers, an Electronic Remittance Advice. Buried in that document are standardized codes that tell you precisely why the insurer refused payment. Claim Adjustment Reason Codes (CARCs) give the reason for the adjustment, and Remittance Advice Remark Codes (RARCs) add context.² CARC 197, for instance, means precertification or authorization was absent when the insurer processed the claim.³

These codes decide your strategy. Denials generally fall into three groups. Administrative denials come from data problems: lapsed eligibility, a wrong policy number, mismatched demographic information. These are usually the easiest to fix and often need only a corrected claim. Clinical denials are harder; the insurer reviewed the service and decided it wasn’t medically necessary under its coverage criteria, and reversing that takes medical evidence, not corrected paperwork. Technical denials sit in the middle, where the service is covered but a procedural requirement was missed, such as missing prior authorization or late submission.

Before writing anything, pull the claim ID, the dates of service, the billed amount, and the specific denial code off the EOB. Every page you send after this should reference the claim ID and the code. Appeals departments handle enormous volumes of paper and electronic files; documents without identifiers get separated and lost.

The Deadlines That Can End Your Appeal Before It Starts

One number matters more than any other: 180 days. Under federal rules governing group health plans and ACA-compliant individual plans, insurers must give you at least 180 days from the date you receive a denial notice to file an internal appeal.¹ Miss it and you lose the right to appeal through the plan’s internal process. Some plan documents set their own window; it may be shorter than 180 days only if it still meets the federal floor.

Once internal appeals are exhausted, a second clock starts. You have four months from the final internal denial to request external review.⁴ If the four-month mark lands on a nonexistent calendar date, it rolls to the first day of the fifth month, and weekends or federal holidays push to the next business day.

Timely filing of the original claim is a separate deadline, and no appeal can save a claim that was never submitted on time. Medicare fee-for-service allows 12 months from the date of service, and a claim denied for untimely filing cannot be appealed at all.⁵ Private insurer deadlines are set by the plan contract and run anywhere from 90 days to a year. Calendar every deadline the moment you get a denial notice.

Build the Appeal Packet

An appeal is only as strong as what’s behind it. An administrative denial usually needs a corrected claim with the right data. A clinical or medical necessity denial needs a case.

A direct appeal letter that identifies the patient, claim number, date of service, and denial code, and states clearly why the denial was wrong.
Clinical documentation organized chronologically: progress notes, diagnostic test results, imaging reports, and operative notes from the treating physician.
A medical necessity argument, ideally from the treating physician, explaining why the service was clinically required. Reference the insurer’s own published coverage criteria and cite clinical guidelines or peer-reviewed literature where they apply.
Prior authorization records if the denial code involves missing authorization: approval letters, reference numbers, or phone logs.
The relevant pages from the plan’s Summary of Benefits showing the service is covered.

Put the patient’s policy number and group ID on every page. Address the packet to the insurer’s appeals department, which is almost always a different mailing address or fax line than the one used for standard claims. The denial letter or provider portal lists the right destination.

Submit It So You Can Prove You Submitted It

Most insurers accept appeals through an online portal, by fax, or by mail. The portal is usually fastest. Look for an Appeals and Disputes section under the claims tab, upload scanned PDFs of the complete packet, and save the electronic confirmation. That number is your proof of timely filing.

If you mail a paper appeal, use certified mail with return receipt requested. The signed receipt is a physical record of when the insurer received it, which matters if the insurer later says it arrived late. A fax with a printed confirmation page works for urgent situations but offers less tracking depth. Whatever method you choose, the point is a documented trail showing when you submitted and what was in the envelope.

What the Insurer Owes You in Return

Individual health insurance plans are limited to one level of internal appeal before you can request external review.⁶ Employer group plans can require up to two rounds. In either case the insurer has to meet set response windows.

For post-service claims, where the treatment already happened and you’re disputing payment, the insurer has 60 days from receiving your appeal to issue a decision.¹ For pre-service claims, where approval is needed before treatment, each appeal level shrinks to 30 days.⁷ These are not suggestions. If the insurer blows the deadline without responding, federal law treats you as having exhausted the internal process, which means you can go straight to external review or, for ERISA plans, file suit.

One protection worth knowing while an appeal is pending: if you’re appealing a denial for an ongoing course of treatment, the insurer cannot cut off that treatment during the appeal, so long as the plan provided proper notice.⁶

Expedited Appeals When Health Is at Risk

Standard timelines don’t work when a delay could endanger a patient. If a standard appeal could jeopardize your life, health, or ability to regain normal function, you have the right to an expedited appeal, and the insurer must respond as fast as the medical situation requires and no later than four business days after receiving the request.⁸ A verbal decision over the phone must be followed by written confirmation within 48 hours.

To trigger the faster timeline, say explicitly why the situation is urgent. The treating physician’s statement about medical risk carries the most weight. You don’t have to wait for a formal denial letter if a pre-service authorization was refused. Call the number on the denial notice or insurance card and ask for the expedited process by name.

Peer-to-Peer Review Before the Formal Fight

Before a formal appeal of a clinical denial, many insurers offer a peer-to-peer review: a phone conversation between the treating physician and the insurer’s medical director. The point is to discuss the clinical reasoning, not to make a new decision on the call. The medical director explains why the claim didn’t meet the plan’s criteria, and the treating physician can add context that wasn’t in the original submission.

A peer-to-peer alone won’t reverse a denial. What it can do is reveal exactly what evidence the insurer found missing, which lets you build a far stronger formal appeal. Only the treating physician can participate, not office staff, and most insurers allow one peer-to-peer per denial. Treat it as reconnaissance.

External Review by an Independent Organization

If the insurer upholds the denial through every internal appeal level, external review is next. An Independent Review Organization with no financial relationship to your insurer evaluates the case from scratch. External review is available for denials involving medical judgment, including medical necessity, whether a treatment is experimental, and certain wellness program standards, and it also covers rescissions of coverage.⁶ Denials based purely on eligibility are not eligible.

You have four months from the final internal denial to file the external review request. For standard reviews the IRO has 45 days to issue a decision.⁴ For urgent cases, the decision must come within 72 hours.

The reason external review is worth pursuing: the insurer is legally required to accept the IRO’s decision.⁹ If the independent reviewer overturns the denial, the insurer pays. The patient pays nothing for the review itself; the insurer or state covers the cost.

If the Claim Is Medicare

Medicare fee-for-service has a different appeal structure than private insurance and Medicare Advantage, with five levels, each with its own reviewer and deadline.

Level 1, Redetermination, is filed with the Medicare Administrative Contractor that processed the claim. Decisions typically arrive within 60 days.
Level 2, Reconsideration, is reviewed by a Qualified Independent Contractor. You have 180 days after the MAC’s decision to request it, and the QIC decides within 60 days.
Level 3, an Administrative Law Judge hearing through the Office of Medicare Hearings and Appeals, must be requested within 60 days of the QIC decision. For 2026 the amount in dispute must be at least $200.
Level 4, Medicare Appeals Council review, has a 60-day filing window after the ALJ decision.
Level 5, federal district court, is available if the Council rules against you, the amount in dispute is at least $1,960 for 2026, and you file within 60 days of the Council’s decision.¹⁰

Most Medicare disputes resolve at the first or second level. The dollar thresholds adjust annually, and multiple denied claims can be combined to reach the minimums. The most common mistake is missing the 60-day deadline at a given level.

Track the Appeal and Follow Up

Filing is not the finish line. Insurers lose paperwork, let decisions sit past deadlines, and send requests for additional information with short response windows. Check the insurer’s portal every two to three weeks. If the status is stuck in pending, call the appeals department and document the date, time, representative’s name, and any reference number.

Keep a tracking log from the day the denial arrives. A simple spreadsheet works: date of each action, submission method, confirmation numbers, names of representatives, and what they said. The log catches small problems (a missing signature, a document request) before they turn into final denials. It also becomes your evidence if the insurer misses its response deadlines, which matters because federal law treats missed deadlines as exhaustion of the internal process.¹ At that point you can move to external review immediately or, for ERISA plans, go to court. Portal screenshots and a dated log are what make that argument stick.

1
eCFR. 29 CFR 2560.503-1 – Claims Procedure
2
Centers for Medicare & Medicaid Services. CMS Transmittal 1163 – X12 N 835 Health Care Claim Adjustment Reason Codes
3
X12. Claim Adjustment Reason Codes
4
eCFR. 26 CFR 54.9815-2719T – Internal Claims and Appeals and External Review Processes
5
Centers for Medicare & Medicaid Services. Transmittal 2140 – Time Limits for Filing Medicare Claims
6
eCFR. 45 CFR 147.136 – Internal Claims and Appeals and External Review Processes
7
U.S. Department of Labor. Benefit Claims Procedure Regulation FAQs
8
HealthCare.gov. Internal Appeals
9
HealthCare.gov. External Review
10
Medicare.gov. Appeals in Original Medicare