How long do you have to appeal a Medicare denial?

For Original Medicare, the first level of appeal, a redetermination, must be filed within 120 days of receiving the initial determination. Each later level has its own deadline: 180 days for reconsideration, then 60 days for each level after that.

What is the difference between a corrected claim and an appeal?

A corrected claim fixes a mistake on the claim itself, such as a wrong code or missing information. An appeal asks the payer to change a decision you disagree with, such as medical necessity, and it needs evidence to back it up.

What should a claim appeal letter include?

The patient, member ID, claim number, date of service, and codes; the denial and its reason codes; a short explanation of why the decision is wrong, tied to the payer’s policy; and a list of the documents enclosed.

What happens if the appeal deadline has passed?

Most late appeals are dismissed. Medicare can accept a late appeal for good cause, and some payer contracts allow exceptions, but neither is guaranteed, which is why denials should be worked well inside the window.

How to Appeal a Denied Claim: Steps and Deadlines

To appeal a denied claim, start with the remit. The reason and remark codes tell you whether the claim needs a correction or an appeal: billing errors are corrected and resubmitted, while decisions you disagree with, such as medical necessity, are appealed with evidence. For Original Medicare, the first appeal, a redetermination, is due within 120 days of receiving the initial determination. For commercial plans, your contract sets the provider appeal deadline.

A denial is a decision, and most decisions can be challenged. The work is knowing which ones are worth it, building the case, and getting it in on time. These 5 steps apply to any payer. The deadlines that follow are where Original Medicare and commercial plans part ways.

Step 1: decide whether to correct or appeal

Start with the codes on the remit, not the claim. Our guide to common denial codes explains what each one means.

Correct it when the claim itself was wrong: a typo, a missing modifier, a wrong diagnosis pointer, or missing information such as CO-16. For most commercial payers that means a corrected claim, frequency code 7, that references the original claim number. For Original Medicare, a minor clerical error is fixed through a reopening (opens in a new tab) with your contractor, not an appeal.
Appeal it when you disagree with the payer’s decision: medical necessity (CO-50), an authorization you did obtain (CO-197), a bundling edit on services that were truly distinct, or a timely filing denial when you can prove the claim went out on time.
Let it go when the denial is correct and the claim cannot be fixed. Adjust it under your policy, and fix the process so it does not happen again.

Step 2: gather the evidence

An appeal is only as strong as what is attached to it. Pull together:

The remit, with the reason and remark codes.
The claim as it was sent, and the corrected version if anything changed.
The clinical note, and any results that support the service.
The authorization number and approval, if one applies.
The payer policy or coverage rule you rely on, with the section named.
Proof of timely filing, such as a clearinghouse acceptance report, for a CO-29 denial.

Step 3: write the appeal letter

Keep it short and specific. Reviewers read many of these, and the ones that win make the case in a few paragraphs. A good appeal letter includes:

The patient’s name, member ID, claim number, date of service, and the codes billed.
The denial you are appealing, with its reason and remark codes.
Why the decision is wrong, in 2 or 3 sentences, tied to the payer’s own policy or your contract.
A list of the documents enclosed.
The name and contact details of the person handling the appeal.

Use the payer’s appeal form when it has one. For Original Medicare, a redetermination request (opens in a new tab) goes in writing, on form CMS-20027 or in a letter with the same information, to the contractor that made the initial decision.

Step 4: meet the deadline

Appeal deadlines are strict, and a late appeal is usually dismissed however good the case is. They differ by payer.

Original Medicare

Original Medicare has 5 levels of appeal (opens in a new tab). Each deadline counts from the day you receive the previous decision.

Diagram of the 5 levels of a Medicare Part A and B appeal: redetermination by the Medicare Administrative Contractor within 120 days, reconsideration by a Qualified Independent Contractor within 180 days, a hearing or review by the Office of Medicare Hearings and Appeals within 60 days with at least $200 at stake in 2026, Medicare Appeals Council review within 60 days, and judicial review in federal district court within 60 days. — The 5 levels of a Medicare Part A and B appeal, with their filing deadlines.

Level 1, redetermination by your Medicare Administrative Contractor (MAC). File within 120 days of receiving the initial determination. The MAC generally decides within 60 days.
Level 2, reconsideration by a Qualified Independent Contractor (QIC). File within 180 days of receiving the redetermination. The QIC generally decides within 60 days.
Level 3, a hearing or review by the Office of Medicare Hearings and Appeals (OMHA). File within 60 days of receiving the reconsideration. In 2026, at least $200 has to remain in dispute (opens in a new tab).
Level 4, Medicare Appeals Council review. File within 60 days of receiving the OMHA decision.
Level 5, judicial review in federal district court. File within 60 days of receiving the Council’s decision, with a higher minimum amount in dispute.

Commercial and Medicare Advantage plans

For a commercial plan, your payer contract and provider manual set the provider appeal deadline, the number of appeal levels, and where to send them. Check them first, because they are often shorter than Medicare’s. Medicare Advantage plans run their own appeal process too, so check the plan’s provider manual rather than assuming Original Medicare’s.

A patient on an ACA-compliant plan can also appeal on their own behalf. According to HealthCare.gov (opens in a new tab), the patient must file an internal appeal within 180 days of receiving notice of the denial, and the plan must decide within 30 days for a service not yet received, or 60 days for one already received. If the plan still says no, the patient can usually ask for an independent external review.

Step 5: track it, and learn from it

Log every appeal with the date it was sent, its deadline, and the outcome. A payer that keeps upholding the same denial is telling you something about your claims or your contract. The overturned ones are telling you something too: if an appeal wins every time, the claim should have been right the first time, and the fix belongs in denial prevention, not in a better letter.

Where Heron fits

Heron works denials inside the appeal window. It names the root cause in plain language, drafts the appeal with the documentation attached, and follows it with the payer to a decision, while your billers keep final sign-off. Denial intelligence then shows which denials keep coming back, so the next fix happens before the claim goes out. For claims already close to a deadline, see aged A/R recovery.

How to appeal a denied claim.