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.

Original Medicare denied a service, and now the provider billed you for it? What the rule says and how to appeal.

Checked against the current rules on September 24, 2026.

A denial for a service, and now the provider billed you for it isn't the end of the story — Original Medicare has to follow specific coverage rules, and a denial that doesn't square with those rules is exactly the kind of appeal 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 a service, and now the provider billed you for it under Original Medicare is governed by§ 411.400 Payment for custodial care and services not reasonable and necessary. and§ 411.404 Criteria for determining that a beneficiary knew that services were excluded from coverage as custodial care or as not reasonable and necessary. and§ 411.408 Refunds of amounts collected for physician services not reasonable and necessary, payment not accepted on an assignment-related basis.. 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 you sign an Advance Beneficiary Notice (ABN) before you got this specific service?
If you did sign one, did it specifically name this service, or was it a blanket notice covering "whatever Medicare doesn't pay"?

What a winning appeal has to show

An appeal that wins usually includes:

A copy of the ABN if one exists, or your own statement that none was given — Without a valid, written ABN given before the service, specifically naming it, the provider — not you — is the one who's considered to have known Medicare might not pay, and generally can't collect from you (42 CFR §§ 411.404, 411.408(d)(2)). (You or your family provide this.)42 CFR 411.404
The Medicare Summary Notice line showing the denial and the "you may be billed" amount — The MSN itself is the record of what was actually denied and why — the bill from the provider needs to match a specific denied line, not a separate charge like a deductible or coinsurance you do owe. (You or your family provide this.)

Your deadline to appeal

120 days from the date on the Medicare Summary Notice — 120 calendar days from when you receive it (42 CFR § 405.942(a)), with receipt presumed to be 5 days after the notice's own date unless shown otherwise.42 CFR 405.942

Your Medicare contractor itself then has its own clock to decide. 60 calendar days from when the MAC receives your timely request. Each time you submit new evidence after filing, that 60-day clock is extended by up to 14 more calendar days for that submission (42 CFR § 405.950(a), (b)(3)) — this can happen more than once.

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 24, 2026

§ 411.400 Payment for custodial care and services not reasonable and necessary.as of September 24, 2026
§ 411.404 Criteria for determining that a beneficiary knew that services were excluded from coverage as custodial care or as not reasonable and necessary.as of September 24, 2026
§ 411.408 Refunds of amounts collected for physician services not reasonable and necessary, payment not accepted on an assignment-related basis.as of September 24, 2026
42 CFR 405.942as 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.