Why Your Plan May Not Pay, and What Depends on Which Plan You Have

A refusal to pay is not one decision made by one kind of organisation under one rule.

The short version, before the detail. Four categories are worth checking for in a denial letter, and the letter should say which one applies rather than leaving you to infer it. They are not an exhaustive list of everything a plan can say; they are the four that lead to clearly different next steps. The category is excluded from the plan altogether; the plan accepts the category but judges it not medically necessary in your case; the plan classifies the use as investigational or experimental; or a different reimbursement rule applies, such as one governing how or where the service was billed. These lead to different arguments and different next steps. Which explanation matters to you depends on which kind of plan you have, because the rules that apply to it are not the rules that apply to the person sitting next to you in the waiting room.

So there are two facts to establish before anything else: your plan type, and the exact reason stated in the letter. Everything below is in service of those two.

What this page can and cannot source, stated before you rely on it. Three parts rest on documents we opened and quote: the Medicare standard from CMS, the tax-account test from the IRS, and the appeal rights of employer group health plans from the Department of Labor. Two parts rest on no payer document at all: what any commercial insurer’s own policy says, and how superbills are assessed. Those two are written as questions to put to your plan rather than as statements of how plans behave, and where you see a question below instead of a rule, that is why. This is the only time the page will say so.

Coverage is not one rule

Four broad situations, governed differently.

Medicare. A federal program with a published determination process.

Medicaid. Federal and state together, so it varies by state.

Commercial insurance. A plan purchased from an insurer, with the insurer’s own policies, subject to the state and federal rules that apply to that plan and that market.

Self-funded employer plans. The employer or the plan bears the claims risk, and may use an insurer or another administrator to run the administration, in which case that company’s name can appear on the card. This is the category to check for rather than assume, because the card can look identical to a commercial policy and can carry an insurer name.

Find out which one you are in. It is in your plan documents rather than reliably on your card, and it determines nearly everything below.

Where to start depends on which of the four you are in. If your coverage comes through an employer, two questions do most of the work: ask your plan or your employer’s benefits contact whether the plan is insured or self-funded, and which appeal process applies to it. If your coverage is Medicare, Medicaid or a policy you bought yourself, that first question does not apply to you; the governing documents for that programme or policy are where the answer lives, and the appeal route comes from there rather than from the insured-or-self-funded split. Either way, get the appeal answer in writing, because the deadline you are working to depends on it.

What Medicare’s standard actually says

For Medicare the standard is published and the wording is specific.

“Medicare coverage is limited to items and services that are reasonable and necessary for the diagnosis or treatment of an illness or injury.”

Source: CMS, Medicare Coverage Determination Process. Accessed 18 September 2026.

Two layers sit underneath that standard.

“National coverage determinations (NCDs) are made through an evidence-based process, with opportunities for public participation.”

and, where no national policy exists:

“In the absence of a national coverage policy, an item or service may be covered at the discretion of the Medicare contractors based on a local coverage determination (LCD).”

Same source.

So for Medicare there can be a national policy, or there can be a local one, and the absence of a national determination does not by itself settle the question. That is a real distinction and it is worth knowing which applies to your situation.

Commercial and self-funded plans set their own policies. Ask whether the policy that applies to your claim is published, and ask for a copy of it either way. A published policy document is a better thing to read than a phone call, because it states criteria rather than an outcome. Ask which policy number applies to your claim.

What “investigational” means to a payer

This word carries the decision, and its meaning inside a policy is narrower than in ordinary use. A word carrying a decision should have a written definition somewhere, and finding that definition is the work of this section.

Ask for the plan’s own definition of the term, in writing, and for the policy document it comes from. A published policy states criteria; a customer service call states an outcome, and the two are not the same thing. If no document is produced, write down that you asked and what you were told instead; an unanswered request is an open item, not a closed one.

Then three follow-up questions, all of which the policy document should answer: which criteria does the plan apply to this category, what evidence would meet them, and when was the policy last revised. That last one matters because a denial issued under an older policy is not necessarily an answer under the current one.

What this page will not do is tell you that the word is a comment on whether a treatment works. We have no document that lets us characterise what any payer means by it.

Read your denial letter

Denial letters state a reason, and the reason determines which door is open.

Not a covered benefit. The category is excluded from the plan. This is a plan design question rather than an evidence question.

Not medically necessary. Read this as the plan having concluded that its own medical-necessity criteria were not met for the service requested. That is narrower than it sounds and it is not the same as the category being excluded, so the first thing to obtain is the criteria themselves. This route turns on what your clinical record shows against them.

Investigational or experimental. Check how the applicable policy defines this term before reading anything into it, because the definition is the plan’s own and it is what the decision turned on.

These three sound similar and lead to different arguments. Identify which one you received before doing anything else.

The appeal route: what to establish before you write anything

For one large category of plan, this is not guesswork. If your coverage comes through a private-sector employer group health plan governed by ERISA, the US Department of Labor publishes what the plan owes you, and four of its statements are worth having in front of you.

Read the boundary of that category first, because the Department states it plainly and an employer plan is not automatically inside it:

“The rules for health claims discussed in this booklet generally apply to people who receive health benefits from a private-sector employment plan. However, there are exceptions for plans sponsored by government or most religious bodies. If you’re not sure whether ERISA applies to you, contact your plan administrator for more information.”

Source: US Department of Labor, EBSA, “Filing a Claim for Your Health Benefits,” archived copy stamped 8 June 2026.

A plan sponsored by a government employer, or by most religious bodies, sits outside these rules even though it arrives through an employer in exactly the same way. Note the Department’s own instruction for the uncertain case: ask the plan administrator. That is the question to ask before you rely on anything in this section.

On how long you have:

“you have at least 180 days to file an appeal (check your Summary Plan Description or claims procedure to see if your plan provides a longer period)”

On the plan’s deadline, and on who controls it:

“A plan may extend the timeline for reviewing an appeal with the claimant’s consent. The plan cannot extend the deadline without your consent.”

On what you are entitled to receive:

“The plan must provide you copies of documents, records, and other information”

And on getting the rules themselves:

“If you do not have a copy of your plan’s Summary Plan Description or claims procedures, contact your plan’s administrator, who is required to provide you with a copy.”

A second set of rules exists, and it does not reach every plan. The four statements above come from the general part of the DOL page. There is a further section headed Additional Rules for Plans Not Grandfathered under the Affordable Care Act, and DOL defines that group:

“Plans that are not grandfathered are those established, or that have made certain significant changes, after March 23, 2010.”

Inside that section, and only inside it, sits the external-review provision. Plans in that group, or their insurers, must:

“Allow you to begin the external review process if the plan fails to follow the internal claims requirements (unless the plan’s violation is minimal)”

So external review is not a general consequence of a plan mishandling its internal process. Whether it is available to you depends on whether your plan is grandfathered, which is a fact about your plan and not something this page can tell you. Ask your plan whether it is grandfathered, and read the denial notice, which for non-grandfathered plans is required to describe the internal and external appeal processes available.

Source for this whole section: US Department of Labor, Employee Benefits Security Administration, “Filing a Claim for Your Health Benefits.”

Scope and access, both stated because both matter here. Scope: the page describes private-sector employer-sponsored group health plans governed by ERISA. It does not describe Medicare, Medicaid, a plan sponsored by a government employer or by most religious bodies, or a policy you bought yourself; if your coverage is one of those, none of these figures are yours. Within it, the four statements above the external-review one come from the general rules; the external-review statement comes from the non-grandfathered section and we have marked which is which rather than presenting them as one set. Access: we read an archived copy of the page, stamped 8 June 2026, rather than the live page. Open the live page yourself before relying on any of it.

What this changes about the section below. Two of the four things to find now have a published answer for ERISA plans rather than only a question: the deadline has a floor, and the documents have to be given to you. The other two still depend on your own plan.

Four things are worth finding before you write a word of the appeal itself:

The deadline. It should be stated in the denial letter. If you cannot find it, ask the plan for it in writing, and ask on what date the clock started.

The levels. How many stages the process has, and whether any stage is handled outside the plan.

What you are allowed to submit. Whether additional clinical documentation can be added, and by whom.

The exact reason being appealed. Which is why the section above comes first.

If the denial letter does not make all four clear, that is itself the first request to send. Get the process described to you in writing before you argue about the substance, because the process determines what arguing is even available.

Superbills: ask the prior question

A superbill is an itemised receipt you submit yourself for possible reimbursement. If a practice offers you one, that offer is easy to hear as a signal that reimbursement is likely.

Two questions are available and the order matters. One is can you give me a superbill? The other is is this service covered by my plan at all, and under which policy? The second comes first, and it goes to the plan rather than to the practice. Get that answer before paying rather than after.

The reason for the order: the paperwork you submit is not what decides the claim.

HSA and FSA: two accounts, two different tests

Tax advantaged accounts have their own eligibility rules, separate from whether a plan covers something. This section has a named authority you can open, and the first thing it shows is that an HSA and a health FSA are not governed by the same sentence. Treating them as one account is the common mistake and it points in the wrong direction.

For an HSA. The IRS defines the term by reference to the tax code, not to your plan:

“In general, ‘qualified medical expenses’ means amounts paid by the HSA beneficiary for ‘medical care’ (as defined in Code section 213(d)) for the individual, the spouse of the individual, and any dependent of the individual, but only to the extent the amounts are not compensated for by insurance or otherwise.”

There is also a timing rule that catches people out:

“For HSA purposes, expenses incurred before you establish your HSA aren’t qualified medical expenses.”

For a health FSA. Here the plan document does enter the test:

“Qualified medical expenses are those specified in the plan that would generally qualify for the medical and dental expenses deduction.”

Source for all three: IRS, Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans. Accessed 18 September 2026. The first two sentences are from the HSA chapter, the third from the health FSA chapter.

What the difference means in practice. For an HSA, the question is whether the expense is medical care under section 213(d) and was incurred after the account existed; your plan does not define it. For a health FSA, there is a second gate: the plan’s own list. So “my plan does not list it” is a relevant answer for an FSA and is not the governing question for an HSA.

This page does not tell you what qualifies in your case. Two questions get a usable answer, and now you know which one to ask about which account: for an FSA, is this expense specified in the plan; for an HSA, is this medical care under 213(d) and incurred after the account was established. Either way, ask what documentation is required, and ask before paying rather than after.

What a coverage decision is not

A coverage decision can turn on plan design, on evidence or medical-necessity criteria, on eligibility, or on reimbursement, coding, network and procedural rules. Which of those it turned on is what the denial letter should tell you, and it is the thing to establish before anything else. What it is not is a clinical verdict on your situation, and it is not a statement that a treatment is worthless.

It also runs the other way. Coverage does not establish that something will work for you, and a plan paying for something is not a clinical endorsement of it for your case.

Where to go from here

If you are going to pay directly, the question becomes what the real total is rather than the quoted figure: The Price You Are Quoted Is Not Always the Total. If the classification in your denial letter turns on evidence, the evidence itself is worth reading: Reading the Study a Clinic Shows You.

Before you leave this page: find your plan type and the exact reason stated in the denial letter. Those two facts determine every step after this one.

What this does not mean

This page does not tell you whether any specific treatment will be covered, does not predict the outcome of an appeal, and does not give tax or financial advice. Coverage rules differ by plan, by state and over time, and the documents that govern your plan are the authority for your situation.

Official sources cited on this page. Every quotation above is taken from one of these. Coverage material ages faster than most, so the date beside each link matters as much as the link.

CMS · Medicare Coverage Determination Process · accessed 18 September 2026
IRS · Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans · accessed 18 September 2026 · the tax-account test
US Department of Labor, EBSA · Filing a Claim for Your Health Benefits · the appeal rights of private-sector employer group health plans governed by ERISA, and the booklet’s own statement of that boundary. We read an archived copy stamped 8 June 2026; the link above is the live page and you should open it

Sources this page still does NOT have, named so you can see the gap: no commercial insurer’s own coverage policy, and no document describing how a self-submitted claim is assessed. Those two sections ask questions rather than state rules, and that is why. The DOL source above covers ERISA employer group health plans only; it is not a source for Medicare, Medicaid or an individually purchased policy, and the section that quotes it says so.

Written and fact-checked against the sources above on 18 September 2026. No independent expert review has taken place yet, and this page says so rather than implying one. This page is reviewed every twelve months.