Glossary
Redetermination
The first level of appeal in Original Medicare — filed with the Medicare Administrative Contractor (MAC) that handled the claim.
Also known as: Level 1 Medicare appeal
Quick answer
A Redetermination is the first appeal step for an Original Medicare claim denial. You file it with the MAC named on your Medicare Summary Notice (MSN), typically within 120 days of receiving the MSN. The MAC re-reviews the claim with any new evidence you submit. CMS Form 20027 is the standard request form.
Why it matters
Most Original Medicare appeals start and resolve at this level. Filing well here often makes higher levels unnecessary.
Why this matters at age 65
TFL claims are typically held by WPS until Medicare resolves the appeal. Reversing the Redetermination usually triggers TFL's secondary payment automatically.
When you'll encounter it
After any Original Medicare denial on the MSN.
Impact on Medicare
First step in the Original Medicare appeal ladder.
Impact on TRICARE For Life
WPS generally cannot process TFL secondary until Medicare's appeal is resolved.
Impact on Medicare Advantage
N/A — MA uses Reconsideration instead.
Common misconceptions
- "Redetermination is the same as Reconsideration." — Different programs. Redetermination = Original Medicare Level 1; Reconsideration = MA Level 1 (or Medicare Level 2).
Common mistakes to avoid
- Sending the appeal to the wrong MAC office.
- Missing the 120-day deadline from the MSN date.
What should I do?
- 1Use CMS Form 20027 or follow the MSN's appeal instructions.
- 2Attach the provider's clinical documentation supporting the service.
- 3Send by traceable mail and keep a copy of everything.
Continue learning
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- Appointment of RepresentativeA signed form (CMS-1696) that authorizes another person — family member, attorney, or advocate — to file or pursue a Medicare appeal on your behalf.
- AppealA formal request to review and reverse a denial, partial payment, or coverage decision by Medicare, a Medicare plan, TRICARE/TFL, VA, or a drug plan.
- Benefit Period (Part A)The Part A timeframe used to measure hospital deductibles and coinsurance — it resets after 60 days out of the hospital.
- Billing ErrorsMistakes — accidental or intentional — on Medicare or TFL claims, ranging from duplicate charges to outright fraud.
- Claim AppealThe formal process for asking Medicare or TFL to reconsider a denied or underpaid claim.
- Coverage DecisionA formal decision by a Medicare Advantage or Part D plan about whether — and how — it will cover a service, item, or prescription.
- Medicare denied a service. Can I appeal?Yes. The first level for Original Medicare is a Redetermination filed with the Medicare Administrative Contractor (MAC) within 120 days of the denial notice (MSN).
- What do I do if my Medicare claim is denied?Read the MSN denial reason, gather supporting records, and file a Redetermination with the Medicare Administrative Contractor within 120 days.
- Do I appeal to Medicare or to TFL?Appeal to whichever payer issued the denial. If Medicare denied, appeal Medicare. If WPS denied TFL's share, appeal to WPS.
- I'm turning 65. What should I do first?About 3 months before your 65th birthday, sign up for Medicare Parts A and B at SSA.gov. TRICARE For Life activates automatically once both are effective and DEERS is current.
- TFL denied a claim. How do I appeal?WPS handles TFL appeals. File a written reconsideration with WPS within 90 days of the denial. Include the Medicare EOB, the WPS denial, and any supporting medical records.
Related glossary terms
Related Official Resources
Continue learning straight from the source. Every link below goes to an official government or DoD resource.
Last reviewed January 2026 against the 2026 Medicare & You and TRICARE For Life handbooks.