Why did my fax fail, and how to fix it

Updated October 25, 2026 · PlusFax team

Busy, no answer, wrong number, no fax tone, partial transmission: what each fax failure means, the likely cause and the fix that works most often.

First, what a failed fax is

A fax is a phone call. It fails for the same reasons a phone call fails: nobody picks up, the line is busy, the number is wrong, or the connection breaks halfway. The difference is that after the call connects, two machines have to agree on a speed and acknowledge every page, so there are a few extra ways for it to go wrong. The status page and the email report name the reason. Here is what each one means and what to do.

Busy

What it means: the receiving line was engaged, either by another fax, by a voice call on a shared line, or because the machine is off hook.

What happens automatically: we redial several times over the following minutes. Most busy faxes are delivered on the second or third attempt without you doing anything.

If it stays busy: the office may share one line between phone and fax, or the machine may have a paper jam that left it off hook. Phone the office and ask them to check the machine, or ask for a dedicated fax line.

No answer

What it means: the number rang and nothing picked up. Fax machines answer within a few rings around the clock, so a genuine no-answer usually means the machine is switched off or unplugged, or the number is a voice line that rang out.

What to do: check the number against the recipient's letterhead or website, and confirm it is a fax line. If it is, ask the recipient whether the machine is on. Resend once that is confirmed.

No fax tone, or answered by a person

What it means: the call was answered, but not by a fax machine. A receptionist picked up, a voicemail greeting played, or an automated phone menu answered.

What to do: you have the office's voice number, not the fax number. Look for a line labelled "Fax" on their website or ask them. This is the most common failure for faxes to clinics and government offices, which publish several numbers side by side.

Invalid or unreachable number

What it means: the number does not exist in the format you entered. The carrier rejected it before the call was placed.

What to do: for domestic numbers, check the area code and that you have all the digits. For international numbers, nearly every case is the leading zero of the area code left in, or the country code entered twice. The international fax guide has the right format for each country.

Negotiation failed, or communication error

What it means: the machines connected but could not agree on how to talk, or lost each other during the handshake. Causes are a noisy line, a VoIP line on the receiving end that compresses audio in a way fax cannot survive, or an old machine that only supports a very low speed.

What happens automatically: we retry, and on retry the connection is negotiated more conservatively, which succeeds more often.

If it keeps failing: tell the recipient; the problem is on their line and will affect every fax they receive. If they have a second number, use it.

Partial transmission: only some pages arrived

What it means: the call dropped mid-document. The pages that were acknowledged before the drop are on the recipient's machine; the rest are not. The report tells you how many pages were confirmed.

What to do: resend the whole document, or just the missing pages with a short cover note. A long, image-heavy document is more likely to hit a dropout; splitting it into two faxes helps. Scans at normal (not fine) resolution transmit faster and drop less. The timing guide explains what makes a page slow.

Document could not be processed

What it means: the file could not be turned into fax pages. Usually a password-protected PDF, a corrupted file, or a file that is not really a PDF or image despite its name.

What to do: open the file on your device and export or print it to a fresh PDF, remove the password, and upload again.

Are you charged for a failed fax?

No. A fax that does not reach the receiving machine is not billed. Account holders are refunded to their balance or plan allowance automatically. A guest payment for a failed fax is refunded on request through the status page or the contact form; see the refund policy.

Before you resend: a checklist

• Is it the fax number, not the phone number?
• Does it have the area code, and for international numbers the country code without the leading zero?
• Is the receiving office open and the machine on?
• Is the document a plain PDF without a password?
• If it dropped mid-way, can you split it or lower the scan resolution?

Then send again from the Send a fax page. The status page will show the new attempt live.

Frequently asked questions

Related guides

• How long does a fax take to send? · Realistic timings per page, what slows a fax down, and when the confirmation arrives.
• How to send a fax to another country · Number format, the trunk-zero rule, a country code table and typical delivery times abroad.
• How to send a fax online · The four steps from a PDF on your screen to a confirmed delivery, and what to check before you press send.
• How to receive faxes online · Getting a fax number that lands in your inbox: local or toll-free, porting an old number, what to expect in a plan.