Reviewed August 2, 2026

Medicare redetermination

The first level of appeal when a party disagrees with an Original Medicare Part A or Part B coverage or payment determination.

Plain-language definition

A redetermination is a new review of an Original Medicare claim decision by Medicare Administrative Contractor personnel who were not involved in the initial determination. It is requested in writing and does not require a minimum dollar amount in dispute.

Where the term appears

A beneficiary sees the initial decision and appeal instructions on the Medicare Summary Notice. Providers and suppliers receive claim information on a remittance advice. The request goes to the MAC that made the initial claim decision.

Deadline

CMS states that the request generally must be filed within 120 days after receipt of the initial determination. Receipt is presumed 5 calendar days after the notice date unless evidence shows otherwise. The specific MSN gives the filing date and address to use.

What the request contains

The written request identifies the beneficiary, Medicare number, disputed item or service, date of service, and reason for disagreement. Supporting evidence may be attached. A person may follow the instructions on the MSN or use Form CMS-20027.

Difference from reconsideration

In the Original Medicare claim-appeal sequence, redetermination is level 1 and is handled by the MAC. Reconsideration is level 2 and is handled by a Qualified Independent Contractor after an unfavorable redetermination. The word “redetermination” is also used in some Medicare drug-plan appeal materials, but those plan appeals follow a different notice and process.

Practical example

An MSN says Medicare did not cover a medical item. The beneficiary believes the item met Medicare coverage rules and submits a written explanation and provider records to the MAC by the date on the MSN. The MAC's new review is the redetermination.

Official sources

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