Can your Medicare contractor just say it's "not medically necessary" with no further explanation?

The denial notice has to explain the basis for the decision and tell you how to appeal. If it doesn't point to a specific rule or criteria, that's itself worth raising in your appeal — you're entitled to know what standard was applied.

What if I don't have all the evidence listed above?

Include what you have. An appeal with partial evidence and a clear explanation of the rule still gets a real review — it doesn't need to be complete to be worth filing.

Missed the window to appeal an old observation stay? A good-cause late request may still work.

Checked against the current rules on September 23, 2026.

The standard retrospective window for a pre-Feb. 14, 2025 observation stay closed January 2, 2026 — but that isn't necessarily the end of it. A late request filed for good cause is still a real path, and one of the 9 recognized good-cause reasons applying to your situation is exactly the kind of case that tends to win.

Here's what the rule actually requires, what evidence usually turns a denial around, and the deadline you're working against.

What the rule requires

Coverage for your chance to appeal a past observation stay (before Feb. 14, 2025) under Original Medicare is governed by§ 405.931 Scope, basis, and definitions. and§ 405.932 Right to appeal a denial of Part A coverage resulting from a change in patient status. and§ 405.942 Time frame for filing a request for a redetermination.. Original Medicare generally cannot apply a stricter test than what these rules require.

Questions that decide it

Before you appeal, these are the facts that usually decide whether a denial like this holds up:

Did a serious illness prevent you from contacting the appeals reviewer?
Was there a death or serious illness in your immediate family?
Were important records destroyed or damaged by a fire, hurricane, earthquake, or flood?
Was access to your records affected by an emergency or disaster?
Did the contractor or appeals reviewer give you incorrect or incomplete information about when or how to file?
Did you not receive notice of the determination or decision at all?
Did you submit a request to a government agency in good faith within the time limit, but it didn't reach the appeals representative in time?
Did you need documents in large print, Braille, or another accessible format, causing a delay?
Did a physical, mental, educational, or language limitation delay or prevent you from filing on time?

What a winning appeal has to show

An appeal that wins usually includes:

A short written statement of the good-cause reason for filing late — The 365-day retrospective window closed January 2, 2026 — a late request needs the good-cause standard at 42 CFR 405.942(b). (You or your family provide this.)42 CFR 405.942
Any record supporting the good-cause reason itself — a death certificate, a hospital admission record, a police or disaster report — A specific, documented good-cause reason is far more likely to be accepted than an undocumented statement alone. (You or your family provide this.)

Your deadline to appeal

By the deadline stated on your notice — see the fast-appeal page for the exact rule for your situation.42 CFR 405.1202

Your Medicare contractor itself then has its own clock to decide. 1 calendar day (observation, hospital discharge) or 72 hours (SNF/home health/hospice ending), once the QIO has what it needs.

Questions people ask

Can your Medicare contractor just say it's "not medically necessary" with no further explanation?: The denial notice has to explain the basis for the decision and tell you how to appeal. If it doesn't point to a specific rule or criteria, that's itself worth raising in your appeal — you're entitled to know what standard was applied.
What if I don't have all the evidence listed above?: Include what you have. An appeal with partial evidence and a clear explanation of the rule still gets a real review — it doesn't need to be complete to be worth filing.

Sources — last checked September 23, 2026

§ 405.931 Scope, basis, and definitions.as of September 23, 2026
§ 405.932 Right to appeal a denial of Part A coverage resulting from a change in patient status.as of September 23, 2026
§ 405.942 Time frame for filing a request for a redetermination.as of September 23, 2026
42 CFR 405.1202as of September 23, 2026

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By CaseWhy Appeals editorial. See how this content is produced. Not legal advice. Not affiliated with or endorsed by Medicare, CMS, or any health plan. A product of CaseWhy LLC.