At a suburban primary care practice on a Tuesday afternoon, a medical assistant slides a two-page referral into a Xerox WorkCentre and dials a fax number handwritten on a manila folder. The office runs Epic. The cardiology group across town runs athenaClinicals. Nobody has the time or budget to build an interface between the two systems for a handful of referrals a week. So the referral goes by fax, gets a “TRANSMISSION SUCCESSFUL” confirmation with a timestamp, and lands in the cardiology group’s incoming-fax queue inside a minute.
What’s remarkable is that nobody finds this remarkable at all.
American doctors keep fax machines near the intake desk not because they fear computers, but because the regulatory, interoperability, and workflow stack underneath them has made fax the last tool that satisfies four constraints at once: no paperwork agreement needed between providers, no shared software required, accepted by federal Medicare and Medicaid workflows, and a defensible receipt on both ends. There are four separate reasons, not one, and they sit at different layers of the system.
The HIPAA seam
The most common misreading is that fax survives on a grandfather clause. It doesn’t. It survives on a specific, active rule about who counts as a “business associate.”
Under 45 CFR 160.103, a business associate is someone who creates, receives, or transmits protected health information on behalf of a covered entity. The law explicitly excludes another provider receiving that information to treat the same patient. HHS’s guidance restates the point: one provider sending records to another provider for that patient’s treatment is not a business-associate relationship.
That carve-out is what makes provider-to-provider fax survive. The primary care office does not need a written agreement with the cardiology group before sending the referral. Cloud storage vendors, secure-email services, and document platforms cannot claim the same carve-out. Hand PHI to any of them and you need a signed Business Associate Agreement, written safeguards, and breach-notification exposure if their controls fail. A fax modem on a phone line sits entirely outside that vendor perimeter. The compliance officer signs off without a second thought. The rule underneath the machine is quietly load-bearing.
For network professionals building or auditing the fax-transmission layer on top of that rule, our HIPAA compliance guide for fax systems is the deeper read.
The CMS submission seam
Federal payers haven’t left fax behind either. Several CMS workflows still accept fax as the primary submission channel today. Durable medical equipment prior authorization can go by fax to Medicare Administrative Contractors. Hospital outpatient department prior authorization still runs the same shape. And Medicare Part D coverage-determination requests go to individual plan sponsors (Blue Cross Blue Shield, HMSA, CarePlus, every plan), each publishing its own fax number on its own coverage-determination page.
The direction of travel is clear: CMS-0057-F, finalized in 2024, requires electronic prior-authorization APIs from covered payers by January 2027. That is a genuine pivot. It applies to a narrow subset of transactions and hasn’t gone live yet. Fax is what fills the workflow today.
The interoperability seam
The largest single reason a piece of paper still exits a fax machine in a clinical setting is that the two electronic systems on either end can’t reliably exchange the record. Interoperability (the ability of different hospital software systems to share information directly) is better than it was in 2017 but nowhere near solved.
ONC’s Data Brief No. 71, published May 2024, found only 43% of non-federal acute-care hospitals routinely completing all four steps of information exchange (sending, receiving, finding, and integrating patient information) across systems in 2023. The other 57% use whatever channel works: a portal, a phone call, or a fax.
Fax fills the seam, and the seam has been slow to close. This is not a US-only pattern. It is why Manitoba doctors process a million fax-based referrals a year and why Australia’s healthcare fax volumes stayed stubbornly high even as its national eHealth agenda pushed electronic exchange.
The audit-trail argument
The last reason rarely gets written about. A fax produces two receipts automatically: the sending machine returns a confirmation with a timestamp and recipient number; the receiving machine logs the incoming transmission with caller ID and page count. Both records exist without either party agreeing in advance to use the same platform.
A clinic that has to prove a record left the building before a prior-authorization window closed can hand an auditor a fax confirmation slip and be done. There is no equivalent one-step proof for an email attachment. The evidentiary value of that receipt (low-tech, immediate, self-generating) is worth more than the aesthetic downside of running a phone line into a Xerox WorkCentre.
The 30-second reframe
The word “still” in “why do American doctors still fax” is doing a lot of unearned work. It implies a modern replacement is sitting on a shelf being ignored. That is not the situation.
There is a specific HIPAA carve-out that makes fax survive between providers without paperwork. There are specific CMS workflows that accept fax today. There is a specific interoperability gap that fax fills when two EHR systems can’t exchange directly. There is a specific evidentiary property fax has that most alternatives don’t. And the federal mandate for electronic replacement, for one narrow workflow, has a January 2027 go-live.
US healthcare fax survives at the regulatory, interoperability, and workflow seams, not at a cultural one. Cultural attachment does exist in some systems. Japan is the well-documented extreme, a story we’ve covered separately. US healthcare is not that story. None of this makes fax good. It makes it load-bearing, in a system that is very slowly building the replacement.
The honest close
PayPerFax is not a HIPAA-compliant, BAA-signing fax vendor. If you are a covered entity looking for the right vendor setup for provider-to-provider PHI transmission, the HIPAA compliance guide for fax systems covers that layer.
Most people who arrived here by searching “why do doctors still fax” need to send one fax to one clinic, once, to close out a records request or file a prior-authorization form. Our pay-as-you-go fax service is priced $0.75 per page after the first, no subscription, and our how-to guide for faxing medical test results covers what a receiving office actually expects on the cover sheet.
The fax machine in that primary care office isn’t going anywhere soon. If you have to send something to it, we can help.