Medicare Fax Number: Where to Fax Medicare Forms

By Michael Chen · Published July 13, 2025 · 12 min read

Quick Answer: There is no single Medicare fax number: 1-800-MEDICARE takes calls and mail, not faxes. Part B enrollment forms (CMS-40B and CMS-L564) and IRMAA requests (SSA-44) go to the fax line of your local Social Security office, Original Medicare appeals go to the contractor named on your Medicare Summary Notice, and Medicare Advantage and Part D requests go to your plan. No fax machine? mFax sends the form from your phone, computer or browser, free for 7 days.

Search for a Medicare fax number and near the top of the results sits Medicare's accessibility notice, a page about braille and large print. Its fax line takes requests for large print and similar formats, not enrollment forms, appeals or claims. Medicare paperwork is split between Social Security, which handles enrollment, the private contractors that process Original Medicare claims, and the insurers that run Medicare Advantage and Part D plans. Each keeps its own fax lines.

Below is where each common Medicare form goes, read on Medicare.gov, CMS.gov, SSA.gov and on the forms themselves on October 26, 2026. You'll also find what to send with a Part B application, what Medicare doesn't take by fax at all, and how to fax any of it without a fax machine.

Is There a Medicare Fax Number?

Not for general questions or for forms. Medicare's contact page lists 1-800-MEDICARE (1-800-633-4227), TTY 1-877-486-2048 and a mailing address, Medicare Contact Center Operations, PO Box 1270, Lawrence, KS 66044. It lists no fax number.

The fax number on Medicare's accessibility notice, 1-844-530-3676, is a line at the Centers for Medicare & Medicaid Services (CMS) for requests for Medicare information in an accessible format, such as braille, large print, or data and audio files. An enrollment form or an appeal sent there lands on the wrong desk.

Everything else goes to whoever handles that part of Medicare:

• Social Security enrolls you. It takes Part B sign-up forms and requests to lower IRMAA, the income-related amount added to Part B and Part D premiums.
• Medicare Administrative Contractors (MACs) process Original Medicare claims for a group of states and handle the first level of appeal.
• Your plan decides coverage and appeals if you're in a Medicare Advantage (Part C) plan or a Part D drug plan.
• The Benefits Coordination & Recovery Center (BCRC) coordinates benefits when you have other coverage, and handles recovery cases tied to liability, no-fault and workers' compensation settlements.

Medicare Fax Numbers at a Glance

The right Medicare fax number depends on what you're sending. Find your row, then read its section below for what goes with it.

Medicare Part B Fax Number: Where to Fax CMS-40B and CMS-L564

Fax them to your local Social Security office. Both forms say so on their first page: the CMS-40B (July 2025 edition) reads "Mail or fax your completed, signed form to your local Social Security office," and the CMS-L564 is sent the same way, together with the CMS-40B. Social Security's Sign up for Part B only page gives the same instruction.

Which forms you need depends on why you're signing up:

• CMS-40B, Request for Enrollment in Medicare Part B. Only for people who already have Part A. It covers your Initial Enrollment Period, the General Enrollment Period (January 1 to March 31) and Special Enrollment Periods.
• CMS-L564, Request for Employment Information. Proof of group health plan coverage through your or your spouse's current employment, for a Special Enrollment Period. You fill in Section A and your employer fills in Section B. The coverage must not have ended more than 8 months ago.
• CMS-10797, Application for Medicare Part A and B — Special Enrollment Period (Exceptional Conditions). For the special situations Medicare recognizes; it goes to the same office, by fax or mail.

How to Find Your Social Security Office's Fax Number

Enter your ZIP code in Social Security's office locator. The office's listing shows its contact numbers, and the fax line is the one marked Fax. If you can't find it, call 1-800-772-1213 (TTY 1-800-325-0778), Monday to Friday, 8 a.m. to 7 p.m., and ask for your local office's fax number. Our guide to Social Security fax numbers walks through both routes.

Some sites still list 1-833-914-2016 as the Part B fax number. It comes from a Social Security blog post from August 2020; Social Security's October 2024 post, its Part B page and the current editions of both forms all send you to your local office instead, so use your office's line.

What to Send With a Part B Application

For a Special Enrollment Period, Social Security asks for three things:

1. The CMS-40B, signed, with "I want Part B coverage to begin (MM/YY)" written in the remarks section, using the month and year you want your coverage to start.
2. The CMS-L564, with Section B completed by your employer. If the employer can't complete it, Social Security's fact sheet tells you to fill in that section as best you can on their behalf and send secondary evidence.
3. One document that proves group health plan coverage in the last 8 months, such as:
   • income tax returns that show health insurance premiums paid
   • W-2s reflecting pre-tax medical contributions
   • pay stubs that reflect health insurance premium deductions
   • health insurance cards with a policy effective date
   • explanations of benefits paid by the group health plan
   • statements or receipts that reflect payment of health insurance premiums

Social Security warns that a Part B application "may be delayed or rejected" if the documentation is incorrect or incomplete. Its fact sheet also lists coverage that doesn't count as coverage based on current employment: COBRA, retiree health coverage, VA coverage and individual plans such as Marketplace coverage. Send the forms and the evidence in one fax, so they arrive together.

Prefer not to fax? Social Security's online Part B application for a Special Enrollment Period takes the same forms and lets you upload the evidence. You sign it electronically, so you'll need an email address.

Fax Number for an IRMAA Reduction (Form SSA-44)

Fax it to your local Social Security office as well. IRMAA, the income-related monthly adjustment amount, is the extra amount people with higher incomes pay on top of their Part B and Part D premiums. If a life-changing event reduced your income, such as marriage, divorce, the death of a spouse, loss of income or an employer settlement payment, Social Security's request to lower IRMAA page says to fill out Form SSA-44 and "fax or mail your completed form and evidence to a Social Security office."

You can also sign in to your Social Security account and upload the request there. If the reason is an amended tax return rather than a life-changing event, Social Security asks you to call 1-800-772-1213 instead.

Medicare Appeal Fax Numbers

There is no central Medicare appeals fax. The first appeal goes to whoever made the decision: the MAC for Original Medicare, or your plan for Medicare Advantage and Part D.

Original Medicare: The Contractor on Your MSN

A first-level appeal, called a redetermination, goes to the MAC that processed the claim. Medicare's Original Medicare appeals page tells you to fill out the Redetermination Request Form (CMS-20027) or write a request, and send it to the address on the last page of your Medicare Summary Notice (MSN). Include:

• your name, address and Medicare Number
• the items or services and the dates you're appealing, or a copy of the MSN with them circled
• why you think they should be covered
• a copy of the Appointment of Representative form, if someone is appealing for you
• anything that supports your case, such as a doctor's note

File by the date printed on your MSN; the CMS-20027 asks for a reason if your notice is more than 120 days old. The MAC generally decides within 60 days. If you disagree, you have 180 days to ask the Qualified Independent Contractor named on your Medicare Redetermination Notice for a reconsideration.

Medicare.gov describes mailing the request. If you'd rather fax it, look for an appeals fax line on your MAC's own website first (the MACs are listed by state below), since not every MAC lists one.

Medicare Advantage: Your Plan's Denial Notice

A Medicare Advantage appeal starts as a request for reconsideration to your plan. Follow the directions on the plan's denial notice, which tell you where to send it, and file within 65 days of the date on that notice. The plan has 30 days to decide on a service you haven't received yet, 60 days on a payment and 7 days on a Part B drug; a fast appeal gets a decision within 72 hours.

Plans publish their own appeal fax lines. Our Aetna fax number guide, for example, lists the lines Aetna's Medicare plans use for medical and Part D appeals.

Part D: Your Drug Plan

For a drug, start with a coverage determination: write your plan a letter, call it, or send CMS's Model Coverage Determination Request form. If the plan says no, ask for a redetermination within 65 days of the denial notice, following its directions. A standard decision takes 7 days for a drug you haven't received and 14 days for a payment; a fast one takes 72 hours.

Each Part D plan, and the pharmacy benefit manager behind it, runs its own fax lines. The Express Scripts and CVS Caremark guides list theirs.

Fast Appeals: Follow the Notice

If a hospital, skilled nursing facility, home health agency, hospice or outpatient rehabilitation facility says your covered services are ending, a fast appeal goes to the Beneficiary and Family Centered Care Quality Improvement Organization (BFCC-QIO) for your state, which Commence or Acentra runs for Medicare. Follow the directions on the notice you were given: the Important Message from Medicare in a hospital, or the Notice of Medicare Non-Coverage elsewhere. In a hospital, ask no later than the day you're scheduled to be discharged.

Medicare Fax Numbers for Providers and Billing Offices

Providers fax their Medicare Administrative Contractor, and each MAC posts its own fax lines, sorted by purpose, on its website. Find your MAC by state below, as CMS listed them on October 26, 2026, then use that MAC's list.

Claims for durable medical equipment, prosthetics, orthotics and supplies (DMEPOS) go to a separate DME MAC:

Home health and hospice claims go to four of the A/B MACs (J6, J15, JK and JM), across four regions that don't match their A/B jurisdictions. CMS keeps the current list and maps on its Who are the MACs page.

For a practice that faxes its MAC and Medicare Advantage plans every week, mFax Business gives the office its own fax number and HIPAA-compliant faxing with a signed BAA, with a confirmed-or-failed status on every fax, on web, mobile and desktop. Plans start from about $9/mo, and you build your own from the seats and pages you need. Our guide to a BAA for a fax service explains what the agreement covers.

Coordination of Benefits and Recovery Fax Numbers

These lines are for Medicare Secondary Payer work: telling Medicare about other coverage, and settling up after a liability, no-fault or workers' compensation case. CMS lists them on its coordination of benefits contacts page, last updated December 17, 2024:

Other inquiries and checks for non-group health plan recoveries that the BCRC started go by mail to P.O. Box 138832, Oklahoma City, OK 73113; CMS lists no fax for them. Customer service for both contractors is 1-855-798-2627 (TTY/TDD 1-855-797-2627), Monday to Friday, 8 a.m. to 8 p.m. Eastern. The same CMS page also points to a portal for submitting documents electronically.

What Medicare Doesn't Take by Fax

Some Medicare paperwork has no fax route at all:

• A claim you file yourself (CMS-1490S). Medicare.gov says you should only need to file a claim "in very rare cases," because the law requires your doctor, provider or supplier to file Original Medicare claims. If you must, mail the form, the itemized bill and supporting documents to the address for your state in the contractor table inside the form.
• Authorization to Disclose Personal Health Information (CMS-10106). This form lets Medicare share your personal health information with someone you name. Submit it online in your Medicare.gov account, or mail it to 1-800-MEDICARE Written Authorization Dept., PO Box 1270, Lawrence, KS 66044.
• Anything for 1-800-MEDICARE itself. It takes phone calls, TTY calls and mail only. For questions about your claims or medical records, Medicare points you to your secure Medicare.gov account or the phone line; records held by a doctor or hospital come from that office, and our guide to faxing a medical records request covers that side.
• The Baltimore address in the fine print. CMS forms such as the CMS-40B and CMS-1490S print a paperwork-burden notice addressed to a PRA Reports Clearance Officer in Baltimore. The forms say not to send applications there; the CMS-1490S warns that doing so "will significantly delay application processing."

How to Fax a Medicare Form Without a Fax Machine

You don't need a fax machine or a trip to a store. mFax sends faxes from the iPhone, iPad and Android apps, from Windows and Apple-silicon Macs, or from any browser at app.mfax.to, and it's rated 4.7 on the App Store and Google Play.

Around 40 seconds a page is normal, and the fax stays In Progress until the last page is through. If it fails, the reason is on the fax in your Sent list: busy lines are retried automatically, while No fax tone means the number didn't answer as a fax line, so check it against your letter. Our guide to a fax that isn't going through covers the rest.

Cover Sheet Checklist for a Medicare Fax

• Address it to the office: "Social Security office" and its city, or the department your letter names.
• Put your name, a callback number and the total page count on it.
• List what's enclosed, for example "CMS-40B, CMS-L564 and two pay stubs."
• Leave your Social Security and Medicare Numbers to the forms, which already ask for them, rather than the cover page anyone at the receiving machine sees first.
• Tick Confidential.

Our guide to a fax cover sheet for medical records shows the layout, and the free cover sheet generator makes one without an account.

Send Your Medicare Form Today

Get mFax on the App Store or Google Play, install mFax for Windows, or open it in your browser. Attach your signed forms, fax them to the number on your letter or in the Social Security office locator, and send them free with the 7-day trial. The fax and its receipt stay in your Sent list while Medicare works on your request.