How to fax a formulary exception with a letter of medical necessity

A formulary exception is a Part D coverage determination: fax the plan's form or the prescriber's letter with a supporting statement that the drug is medically necessary, and the plan decides within 72 hours of receiving that statement, or 24 hours when expedited. CMS counts a faxed statement as received when the transmission report shows it went through.

How do you fax a formulary exception request?

A formulary exception request goes by fax as one package to the Part D plan or its pharmacy benefit manager: the request on the plan's form, CMS's model form or the prescriber's letter, with the prescriber's supporting statement and clinical documentation behind it, sent to the number printed on that plan's current form.

1. Name the exception: a formulary exception, a tiering exception, or a waiver of step therapy or another utilization management rule.
2. Get the prescriber's supporting statement that the drug is medically necessary, on the plan's form, CMS's model form or the prescriber's own letter.
3. Put the request first, with the statement and the relevant clinical documentation behind it.
4. Download a fresh copy of the plan's form and fax the package to the number printed on it.
5. Keep the fax transmission report that shows the pages went through.

42 CFR 423.566 lets the prescribing physician or other prescriber ask for a coverage determination on the enrollee's behalf. CMS's Parts C and D appeals guidance also counts a request from staff of the prescriber's office acting on the prescriber's behalf, such as one on the prescriber's letterhead or one that comes from the prescriber office fax machine.

Which exception are you asking for?

A Part D exception request is a type of coverage determination, and it comes in two kinds: a formulary exception, which also covers a waiver of step therapy or another utilization management rule, and a tiering exception. Each kind asks for something different, and the prescriber's statement must show something different for each.

A tiering exception lets the enrollee get a non-preferred drug in a higher cost-sharing tier at the terms of the lower tier. Under 42 CFR 423.578(b), a formulary exception also reaches a coverage policy such as step therapy, a dosage limit or therapeutic substitution that keeps a Part D drug from being covered.

CMS treats a request to waive a prior authorization or other utilization management requirement as an exception request. A prescriber who simply sends the plan's prior authorization form to satisfy the requirement is making a plain coverage determination request.

What must the supporting statement or letter of medical necessity say?

The supporting statement, whether a form or a letter of medical necessity, must indicate that the requested drug is medically necessary for one of the reasons CMS lists for that kind of exception.

CMS describes the supporting statement as any statement, verbal or written, that indicates the drug is medically necessary. For a formulary exception, CMS lists three reasons, and two of them concern the drugs the formulary already covers. One is that every covered Part D drug on any tier of the formulary would be less effective for the enrollee than the requested drug, would have adverse effects, or both. Another is that the alternatives, or the drugs step therapy requires, have caused or are likely to cause an adverse reaction or other harm.

For a tiering exception, the statement must indicate that the drugs on the lower cost-sharing tier would be less effective than the requested drug, would have adverse effects, or both.

The CMS exceptions page lists a letter prepared by the prescriber as a written supporting statement, beside CMS's model form and a plan's own exceptions form. A plan may not require the request or the statement on a specific form, and CMS's model form instructions say plans must accept any written request for a coverage determination. A prescriber may give the statement orally, and the plan may then require a written one.

An incomplete statement still counts as received and starts the clock. No statement guarantees approval, because the rule says a supporting statement does not produce an automatic favorable decision.

Where does the request go: the Part D plan or the pharmacy benefit manager?

The request goes to whoever decides drug coverage for the enrollee's plan: the Part D plan itself, which must accept requests 24 hours a day, 7 days a week, or the pharmacy benefit manager the plan uses, on that manager's own route. Each route takes exception requests its own way, from its own page.

Optum Rx says its e-PA solution supports all forms of prior authorization and formulary exception requests, and it sends prescribers who can use neither e-PA nor the phone to its listed forms. Optum Rx is retiring most fax numbers used for pharmacy prior authorization requests, except in Massachusetts, Rhode Island, South Carolina and Texas. Its general request form is for non-urgent requests and warns that forms are updated frequently and may be barcoded.

Express Scripts' prescriber page, now hosted by Evernorth, points prescribers to its general request form for a coverage determination such as a step therapy exception and says to fax requests to the number shown on that form; the Express Scripts prior authorization fax number page tracks it. Its Medicare coverage determination form may go by mail or fax.

CVS Caremark's Global Formulary Exception/Prior Authorization Request Form tells the prescriber's office to fax the completed form, and its prescriber page also takes requests electronically or by telephone, depending on the plan. For Medicare Part D, that page sends providers to the plan's own website for the form. The lines are listed on the CVS Caremark prior authorization fax number page.

MedImpact's Medication Request Form covers overrides of step therapy, quantity limits and other edits, and its July 2026 version is for prescribers only and requires the prescriber's signature. Its Part D form goes by mail or fax, with supporting-information pages for the prescriber. Evernorth lists a Colorado step therapy exception form, and MedImpact lists a Colorado Serious Mental Illness Step Therapy Exception Form.

A Medicare Advantage plan can route its Part D requests to a pharmacy benefit manager. Wellmark's manual sends them to CVS Caremark, asks for medical history or other pertinent patient information with a formulary exception, and says any form a provider sends by fax or mail will be worked appropriately. A Part D rule binds the Part D plan, and a commercial route follows its own manager's terms.

When does the clock start, and how long does the plan have?

The clock starts when the plan receives the prescriber's supporting statement, and the plan then has 72 hours to decide a standard exception request and 24 hours to decide an expedited one.

For an ordinary Part D coverage determination, notice is due within 24 hours after an expedited request or 72 hours after a standard one. For an exception, those timeframes do not begin until the plan receives the supporting statement. Under 42 CFR 423.568, if no statement arrives by the end of 14 calendar days from receipt of the exception request, the plan must decide within 72 hours from the end of those 14 days.

CMS counts a request or a supporting statement as received on set dates and times, and for a fax that moment is when the document is successfully transmitted to the plan, as indicated on the fax transmission report. Plans must be able to accept requests 24 hours a day, 7 days a week, holidays included. What a sender can rely on as proof of a send is covered in how to tell if a fax went through.

What delays or sinks an exception request?

An exception request is delayed or lost by a missing supporting statement, a request with drug details and no clinical documentation, an outdated form, or a fax number the manager has retired.

Express Scripts' Medicare form says formulary and tiering exception requests cannot be processed without a prescriber's supporting statement, and the Part D clock does not start until that statement arrives. CVS Caremark's form warns that demographic and drug information alone may not be a sufficient request for coverage and asks for relevant clinical documentation.

Optum Rx's forms change often and may be barcoded, and most of its pharmacy prior authorization fax numbers are retiring. MedImpact's form needs the prescriber's signature. A plan that takes an oral statement may still ask for it in writing.

A plan's own prior authorization form, sent to meet a requirement, is processed as a coverage determination rather than an exception. A denied exception can be appealed, and the Medicare Part D reconsideration fax number page covers where a reconsideration request goes.

How long does an approved exception last?

An approved Part D exception lasts for the rest of the plan year, and the plan may not make the enrollee ask again for a refill or a new prescription of that drug. The approval holds while the enrollee stays enrolled in the plan, the prescriber keeps prescribing the drug, and the drug stays safe for treating the condition.

How do you send exception requests from a HIPAA fax account?

From Fax Pigeon, the request and the prescriber's letter go out as one PDF from the browser or from email. A cover sheet is optional, so the plan's own form can be page one. Every delivered fax gets delivery proof to keep beside the plan's reference number. The BAA is signed at signup on every plan.

* Official sources (CMS, the Code of Federal Regulations, Optum Rx, Express Scripts, CVS Caremark, MedImpact, Wellmark) were read on October 20, 2026. Fax Pigeon prices and plan terms as of October 20, 2026.