What to do with fax when the copper line goes
Fax machines were built for copper phone lines, and they are often the first thing to break when a line moves to the internet. Medical offices, pharmacies, law firms and schools still depend on them. Here are the options.
Updated October 15, 2026 · Twisted VoIP
Why fax struggles off copper
A fax machine sends sound tones that assume a clean, continuous connection. Internet phone service breaks sound into packets, and a few lost or delayed packets, or features like silence suppression and compression, are enough to fail a fax. A protocol called T.38 was designed to carry fax over the internet more reliably, but support differs between providers and equipment, so results vary.
Source: Dialogic white paper on fax over IP.
Your options
| Option | Good for | Watch for |
|---|---|---|
| Online (cloud) fax | Most offices: send and receive by email or a web app; no machine needed | Healthcare needs a provider that signs a business associate agreement |
| Fax machine on a VoIP adapter (T.38) | Keeping existing machines and multifunction printers | Test with the numbers you fax most; reliability depends on the provider |
| Fax machine on a cellular line replacement | Sites already replacing alarm or elevator lines with a device like Ooma AirDial | Test before cancelling the copper line |
In every case you can usually keep the fax number by porting it to the new service.
HIPAA and healthcare
If a fax service stores or processes patient information, it is a business associate under HIPAA and needs a business associate agreement (BAA) with you. Services that only transmit, with nothing more than temporary storage, can fall under the "conduit" exception. Most online fax services store faxes, so ask for a BAA.
Sources: HHS on cloud computing, HHS on the conduit exception.
Steps
- List every fax number on your bills and which machine or device answers each one.
- Decide per number: online fax, or keep the machine on a VoIP adapter or cellular device.
- Port the numbers and test sending and receiving with the places you fax most, including multi-page documents.
- Cancel the copper line after the test.
Is your line on a filing?
Questions
Can I keep my fax number?
Usually yes. Fax numbers can be ported to online fax services and VoIP providers like any other phone number.
Does fax work over VoIP?
It can, especially with T.38 support, but reliability varies by provider and equipment. Test with the numbers you fax most before cancelling the copper line.
Is online fax HIPAA compliant?
It can be, if the provider signs a business associate agreement and protects the data. Ask any provider for a BAA before sending patient information.
Get a plan for your lines
Tell us what runs on your copper lines. We'll check the filings for your address and tell you what we'd replace each line with. No obligation. Prefer to talk? Call 623-307-5548.
Related guides
General information, not legal or code advice. Requirements depend on your state, your local authority and your equipment.