By David Thompson · Published September 2, 2025 · Updated June 8, 2026 · 8 min read
Quick Answer: Fax error codes tell you exactly why a transmission failed. The most common are Communication Error (bad phone line), Busy (recipient in use), No Answer (machine off), and NG (generic failure). Find your error code in the table below for the fix — or skip the troubleshooting and send via mFax.to.
Your fax machine just spit out a page covered in error codes. The document didn't go through, and now you're staring at a cryptic message like "Error 344" or "Comm. Error" with no idea what it means.
Fax error codes are the machine's way of telling you what went wrong. The problem is that every manufacturer uses a slightly different numbering system, and the messages are rarely plain English. This guide decodes the most common fax error codes across HP, Brother, Canon, Ricoh, and Epson machines — and gives you the exact fix for each one.
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Master Error Code Reference Table
Find your error message or code below and jump to the detailed fix.
| Error Code / Message | Meaning | Most Likely Cause | Fix |
|---|---|---|---|
| Busy / 486 | Recipient line is in use | Another fax in progress | Wait 5 min, retry |
| No Answer | Recipient machine didn't pick up | Machine off or auto-answer disabled | Call recipient, confirm machine is on |
| No Fax Tone / No Fax Detected | Dialed a voice line, not a fax line | Wrong number | Verify fax number with recipient |
| Communication Error / Comm. Error | Connection dropped mid-transmission | Bad phone line, VoIP, or line noise | Lower baud rate |
| NG (No Good) | Generic transmission failure | Line noise or incompatible machine | Check line quality, retry |
| ECM Error | Error Correction Mode conflict | Noisy line or VoIP connection | Turn ECM off |
| Error 200–205 | Handshake failure during reception | Poor line conditions | Retry; check phone cable |
| Error 222–237 | Transmission failed (various stages) | Line noise, ECM conflict, timeout | See 200-series fixes |
| Error 312 | Remote machine failed to answer | Machine off, disconnected, or jammed | Contact recipient |
| Error 313 | Remote line is busy | Another fax in progress | Wait and retry |
| Error 344 | Remote machine stopped responding | Connection lost mid-transmission | Retry; check remote machine status |
| Error 345–348 | Buffer overflow or memory full | Document too large or memory full | Send fewer pages per batch |
| Remote Fax Aborted | Receiving machine disconnected | Poor connection or remote jam | Retry; contact recipient |
| Vacant Code Tone | Number is out of service | Disconnected or ported number | Verify number is active |
Manufacturer Differences
HP, Brother, Canon, Ricoh, and Epson each use slightly different error numbering. The codes above cover the most common ones across all brands. Check your machine's manual for brand-specific codes not listed here.
Communication Errors (Comm. Error)
"Communication Error" is the single most common fax error message. It means the two fax machines established a connection but lost it during transmission. On Brother machines, it appears as "Comm. Error" on the LCD. On HP machines, it often shows as error codes in the 220–237 range.
Common causes:
- Poor phone line quality — static, crackling, or weak signal on the line
- VoIP interference — VoIP codecs compress audio and corrupt fax tones (learn more)
- Shared line devices — call waiting, voicemail, or an answering machine interrupting the transmission
- Remote machine issues — the recipient's fax ran out of paper, jammed, or had a memory error mid-receive
How to fix it:
- Lower the baud rate to 9,600 bps in your fax machine's settings (Fax Settings > Transmission Speed). This gives the signal more room for error.
- Check the phone line — pick up a handset on the same line and listen for static. If you hear noise, contact your phone provider.
- Disconnect shared devices — unplug answering machines, disable call waiting (dial
*70before the fax number), and remove any splitters. - On VoIP lines, switch to the G.711 codec and enable T.38 protocol if your provider supports it.
- Retry — sometimes the issue is temporary line noise that clears up in a few minutes.
If communication errors happen frequently, your phone line may not be reliable enough for fax. Consider switching to a cloud fax service that bypasses the phone line entirely.
200-Series Errors (Handshake & Reception)
200-series error codes relate to the fax handshake — the initial negotiation phase where the two machines agree on speed, resolution, and protocol. These errors are most common on older machines and noisy phone lines.
Handshake Failure
The receiving machine failed to detect the initial fax signal. Usually caused by poor line conditions during the critical first 5 seconds of the connection.
Fix: Retry immediately. If it fails again, lower baud rate to 9,600 and try a different phone cable.
Incomplete Page Received
The receiving machine got a partial page but couldn't complete it. ECM attempted to correct the data but ran out of retries.
Fix: Turn ECM off on both machines and retry. If using VoIP, switch to G.711 codec.
ECM Transmission Failure
These codes indicate that Error Correction Mode failed to recover from data corruption. The machines exchanged data but couldn't agree that it was received correctly.
Fix: Disable ECM, lower baud rate to 9,600 or 4,800, and retry. See the ECM section below.
300-Series Errors (Connection & Line)
300-series errors occur at the connection level — before or during the actual data transfer. These are the most straightforward to diagnose.
No Answer from Remote Machine
The receiving fax machine did not pick up the call. It could be powered off, disconnected, jammed, or set to manual receive mode.
Fix: Call the recipient and ask them to confirm their fax machine is on and set to auto-answer. Also verify you have the correct number.
Remote Line Busy
The receiving fax line returned a busy signal, meaning it's currently handling another fax or phone call.
Fix: Wait 5 minutes and retry. Most fax machines have an auto-retry feature — set it to 3–5 attempts at 5-minute intervals.
Remote Machine Stopped Responding
The connection was established, but the remote machine stopped communicating mid-transmission. This is one of the most frustrating errors because it usually means the fax started sending but failed partway through.
Fix: Retry after 5 minutes. If it persists, the problem is likely on the recipient's end — paper jam, memory full, or their phone line dropped. Contact the recipient to check their machine.
Buffer Overflow / Memory Full
The receiving machine's memory is full and cannot accept more data. This happens with large multi-page faxes or when the receiving machine hasn't been cleared.
Fix: Send fewer pages at a time (5–10 per batch instead of 25+). Ask the recipient to clear their fax machine's memory by printing stored documents.
ECM (Error Correction Mode) Errors
Error Correction Mode is a feature built into most modern fax machines. When enabled, it detects corrupted data and requests the sender to retransmit damaged sections. On a clean analog line, ECM improves reliability. On a noisy or VoIP line, it creates an endless loop of retransmission requests that eventually time out.
When to turn ECM off:
- You're on a VoIP line — retransmit requests make things worse
- You see error codes 232–237 repeatedly
- Your fax always fails on the same page mid-transmission
When to leave ECM on:
- You're on a clean analog phone line
- You're sending sensitive documents where a garbled page is worse than a failed transmission
The setting is usually under Fax Settings > ECM or Error Correction > On/Off. Not sure if your line is analog or VoIP? Check our analog vs. digital fax guide.
ECM Rule of Thumb
Analog line = ECM on. VoIP or noisy line = ECM off. When in doubt, turn it off, retry, and see if the error clears.
Online Fax Error Codes
If you use an online fax service instead of a physical machine, you'll see a different set of error messages. These are simpler because they've already eliminated phone line and hardware issues on your end.
| Error | Meaning | Fix |
|---|---|---|
| Busy | Recipient line in use | Wait and retry |
| No Answer | Remote machine didn't pick up | Verify number; contact recipient |
| Not Accepted Here | Destination doesn't support T.38 fax | Confirm fax number is correct |
| Call Dropped Prematurely | Connection lost mid-send | Retry; likely recipient-side issue |
| Document Error | File format not supported or corrupted | Convert to PDF and retry |
| Far End Cannot Receive | Document too large for remote machine | Send in smaller batches (5–10 pages) |
| Disconnected After Retries | Multiple failed attempts | Check network; try a different time |
Fewer Errors, Better Receipts
Online fax services like mFax eliminate the most common physical fax errors — line noise, ECM conflicts, and VoIP problems — because they use dedicated fax gateways instead of your phone line. You get a clear delivery receipt (or a plain-English error message) for every fax.
When Error Codes Mean It's Time to Switch
If you're seeing fax error codes regularly — especially communication errors, ECM failures, or VoIP-related issues — the problem may not be fixable with settings changes. Here's when the error codes are telling you something bigger:
- Frequent Comm. Errors on VoIP — your VoIP line is fundamentally unreliable for faxing. See our VoIP fax guide for fixes, but cloud fax is the permanent solution.
- Repeated 200-series errors — your phone line quality is degrading. Old copper wiring, distance from the central office, or weather-related damage can cause persistent issues.
- Memory full errors on the receiving end — the recipient's machine is old or overwhelmed. You can't fix their hardware, but you can send via a service that retries automatically.
- Same error to different recipients — the problem is your line or machine, not theirs. A test fax to a known-working number will confirm this.
Online fax services bypass every error on this list that's related to phone lines, hardware, or VoIP. Your document goes from your phone or computer to a dedicated fax gateway over the internet — no phone line on your end at all.
Quick Troubleshooting Flowchart
Not sure where to start? Follow this decision tree:
- Is the error "Busy" or "No Answer"? → Wait 5 minutes, retry. If it keeps happening, call the recipient.
- Is the error "No Fax Detected" or "Vacant Code"? → Wrong number. Verify the fax number with the recipient.
- Is the error "Communication Error" or "NG"? → Lower baud rate to 9,600. Check phone line for static. If on VoIP, switch to G.711.
- Is the error in the 200-series? → Turn ECM off, lower baud rate, retry.
- Is the error in the 300-series? → Problem is on the recipient's end. Contact them to check their machine.
- Does the same error happen to every number you fax? → The problem is your line or machine. Send a test fax to confirm. If the test fails too, your line needs service — or switch to online fax.
If you've exhausted these steps and faxes still fail, read our full fax not going through troubleshooting guide for 8 additional fixes.
Send Your Fax Now
If you're tired of decoding error messages, skip the fax machine entirely. Open mFax.to, upload your document, enter the recipient's fax number, and send. It works from any phone, tablet, or computer — no error codes, no phone line, no guessing.
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