Revenue cycle

Medicare redetermination: how to file one, and what comes after

A redetermination is the first level of appeal in Original Medicare: you ask the MAC that processed the claim to look at it again. You have 120 calendar days from receiving the remittance or notice to file. Before you do, check whether the problem is a clerical error, because those go through a reopening instead.

Redetermination or reopening? Decide first

Medicare requires clerical errors, including minor errors and omissions, to be corrected through a reopening, not an appeal (405.927; 405.980(a)(3)). CMS's list of what counts is broader than many billers expect. It includes misapplication of a fee schedule, so a short payment caused by the wrong rate or a wrongly applied reduction is often a reopening (Claims Processing Manual ch. 34, §10.4).

Two things don't qualify as clerical: adding services you didn't bill the first time, and errors by a third-party payer (§10.4). Part B MACs must offer reopenings by telephone, which suit quick fixes and generally not medical necessity (§10.5).

Reopening is discretionary, though. The MAC's decision on whether to reopen is binding and can't be appealed (405.980(a)(5)). If the MAC decides your issue isn't clerical, it dismisses the request and points you to your appeal rights, but only if the appeal window on the original claim is still open. So if day 120 is close, file the redetermination. CMS tells MACs that when they start handling a timely redetermination as a reopening and can't complete it, they process it as the redetermination you asked for (ch. 34, §10). Once an appeal is pending, no one can reopen that issue until appeal rights run out (405.980(a)(4)).

How to file a redetermination

Send it to the contractor named on the notice. The request must be in writing, on the CMS form or in a letter that carries the beneficiary's name, the Medicare number, the services and dates of service, and the name of the party or representative (405.944(b)). CMS also asks for an explanation of why you disagree (CMS). Portal, fax and mail options differ by MAC, so check your MAC's site.

Most of Form CMS-20027 is identification. The fields a provider should fill with care:

• Field 5: the date of the initial determination notice, with a copy attached. If it's been more than 120 days, give the reason here.
• Field 5b: whether the appeal involves an overpayment (providers and suppliers only).
• Field 6: why you disagree. For a short payment, show the amount you expected and how you got it, from the fee schedule and the date of service. Our guides on expected reimbursement and the underpayment appeal letter cover what to put here.
• Field 8: evidence. You can send it later, but it must reach the MAC before the redetermination issues.

Counting the 120 days

The clock starts when you receive the initial determination, which Medicare presumes is 5 calendar days after the date on the notice unless there's evidence otherwise. All days are calendar days. The request is filed when the MAC receives it, not when you send it (405.942(a)).

Illustrative dates. A remittance is dated March 3, 2026. Presumed receipt is March 8. Day 120 is July 6, 2026, and the MAC must have the request by then. The 1-year reopening window counts from the date of the determination itself, March 3, not from receipt.

A late request needs good cause, shown in writing (405.942(b)). The regulation's examples include serious illness, records destroyed by fire or other accident, wrong or incomplete information from the contractor about how to appeal, and never receiving the notice.

What the MAC does

The MAC must send its decision or dismissal within 60 calendar days of receiving a timely request. Each additional evidence submission extends that by up to 14 calendar days (405.950).

The five levels of Medicare appeals

Each later deadline also counts from receipt, presumed 5 calendar days after the notice date, and every day is a calendar day.

Put all your evidence in by level 2. Unless you show good cause, evidence you don't submit before the QIC issues its reconsideration can't be considered later (405.966(a)(2)). For a provider, the QIC file is effectively the record for every level after it.

Amount in controversy, and why aggregation matters

The thresholds are $100 and $1,000, indexed from 2003 by the medical-care CPI and rounded to the nearest $10 (405.1006(b)–(c)). For requests filed in 2026 they are $200 for an ALJ hearing and $1,960 for court (Federal Register, Dec. 4, 2025). From January 1, 2027, the ALJ threshold stays at $200 and the court threshold rises to $2,000 (Federal Register, Sept. 16, 2026).

The amount is generally the charge minus what Medicare paid and minus any collectible deductible and coinsurance. When the line was paid at the published fee schedule amount and you are challenging that amount itself, it's the difference between the allowable you argue for and the published one (405.1006(d)).

A single short-paid line rarely reaches $200. You can combine claims for an ALJ hearing if the QIC has already reconsidered each one, they involve similar or related services, and you ask within 60 calendar days of receiving all of the reconsiderations. Part A and Part B claims can be combined (405.1006(e)). The same error repeated across many claims is how a small underpayment gets a hearing.

"Reconsideration" means three different things

Part D also uses the word redetermination, for drug plan appeals. That is a separate process and not the one described here.

Medicare Advantage is a different process

If you're not contracted with the plan and it denies payment, you can ask the plan for a reconsideration. The regulation gives 60 calendar days from receipt of the determination, presumed 5 days after its date (422.582(b)). CMS's guidance states the same window as 65 calendar days from the remittance date and requires a signed Waiver of Liability holding the enrollee harmless (CMS Parts C & D appeals guidance). The plan has 60 calendar days to decide, and if it upholds the denial in whole or in part it must send the case to CMS's independent review entity (422.590(b)).

A non-contract provider disputing the amount paid, rather than a denial, uses CMS's payment dispute process; the underpayments guide covers it. If you are contracted with the plan, your contract sets the payment dispute terms, not the Part C reconsideration process (CMS guidance).

Questions

What is the timely filing limit for a Medicare redetermination?

120 calendar days from the date you receive the initial determination. Receipt is presumed to be 5 calendar days after the date on the notice, and the request counts as filed on the day the MAC receives it, so mail time comes out of your window.

What's the difference between a reopening and a redetermination?

A reopening corrects a clerical error, such as a math mistake, a transposed code or a misapplied fee schedule, and can be requested within one year of the determination. A redetermination is the first level of appeal, for disputes such as medical necessity or coverage. Reopening is at the MAC's discretion, and a refusal to reopen can't be appealed.

What are the 5 levels of Medicare appeals?

Redetermination by the MAC, reconsideration by a Qualified Independent Contractor, a hearing before an OMHA administrative law judge, review by the Medicare Appeals Council, and judicial review in federal district court. The last three require a minimum amount in controversy.

Is there a minimum dollar amount to appeal a Medicare claim?

Not for a redetermination or a QIC reconsideration. An ALJ hearing requires $200 in controversy in 2026 and 2027. Federal court requires $1,960 for filings in 2026 and $2,000 for filings on or after January 1, 2027.

How long does a Medicare redetermination take?

The MAC has 60 calendar days from receiving a timely request. Each time you send more evidence after filing, that clock extends by up to 14 calendar days.

Last reviewed October 28, 2026. This guide is general information about payer payment rules, not legal advice. Your payer contract and provider manual control the details; check them before you file.