Fax fails on a VoIP, cable or fiber phone line
Faxing unreliable since your phone line moved to internet, cable or fiber? Lower the fax speed, adjust ECM, use the right adapter port or a fax alternative.
Quick fix
Set the printer's fax speed to its slowest setting, usually 9600 bps, and test with ECM both on and off. Plug the printer straight into the phone port on your provider's modem or adapter, without splitters. If faxes still fail, check whether your provider supports fax on the line, for example through T.38, or use an online fax service or scan to email.
Didn’t work? Go to the full stepsYou might see
- Faxing stopped working after your phone service moved to internet, cable or fiber
- Faxes fail partway, especially longer ones
- Some faxes go through and others fail for no obvious reason
- Received pages arrive garbled, cut off or with missing lines
Usually caused by
- Voice compression that distorts fax tones
- Network delay and lost data that break the fax handshake
- Fax speed too high for a digital line
- Printer plugged into a splitter or a port not set up for fax
- A phone plan or adapter that doesn't support fax
Step-by-step fix
Work through the steps in order and check each one off. Most people are printing again before the last step.
Any printer with a fax
0 of 8 steps tried
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Understand what goes wrong
Digital phone services turn your call into data packets and often compress the sound to save bandwidth. Speech survives this well, but fax tones are precise signals, so compression, delay and lost packets can corrupt them. Slower, simpler fax settings give the call the best chance.
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Lower the fax speed
In the printer's advanced fax settings, set the fax or modem speed to 9600 bps, or 14400 bps if 9600 isn't offered. Some printers label these slow and medium. Slower speeds are more tolerant of the small errors digital lines introduce.
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Try ECM on and off
Error correction mode (ECM) resends damaged parts of a page, which helps on noisy lines, but on some digital lines the extra back-and-forth makes calls fail. Send a few test faxes with ECM on, then with it off, and keep whichever works. Some printers have one VoIP or basic compatibility setting that lowers the speed and adjusts ECM together.
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Use the right phone port
Plug the printer's LINE port straight into the phone port on your provider's modem, router or adapter box, without splitters, DSL filters or extension cords in between. If the box has two phone ports, your provider may have set one up for fax, so check the label or the provider's documentation.
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Send less data per fax
Color and fine or photo resolutions send far more data, which raises the chance of an error. Send in black and white at standard or fine resolution, and split long documents into a few shorter faxes.
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Check whether your provider supports fax
Look in your phone provider's help pages or account, or ask its support through its website, whether the line supports fax. Good signs are T.38, a standard for carrying fax over internet calls, or an uncompressed voice codec such as G.711. Some providers offer a fax-ready port or plan.
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Turn off extra line features
Call waiting, call forwarding and voicemail on the fax number can interrupt or intercept fax calls. Turn them off for that number in your phone account settings if you can.
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Use an alternative to the phone line
If faxing still fails, an online fax service sends and receives faxes over the internet through a website, app or email, with no phone line needed. For recipients who accept email, scan to email or scan to PDF and attach the file, which is often faster and clearer.
Did this fix it?
Good. To confirm everything is healthy, print a test page. It takes a minute and shows any quality problems early.
Try these next
Still stuck? The troubleshooter asks a few questions and narrows it down. If your printer is under warranty, the manufacturer can repair or replace it at no cost. Find their official support site on our brand pages.
Common questions
Why did my fax stop working when my phone line changed?
Many providers have moved home and business lines from copper to digital services. These are designed for voice, and fax tones don't always survive the compression and delays they add.
What is T.38?
T.38 is a standard that carries fax over internet phone networks as data rather than as sound, which is much more reliable. Whether you can use it depends on your provider and equipment.
Is 9600 bps too slow?
A typical text page still usually takes well under a minute at 9600 bps, so the difference is small, and far fewer faxes fail.