Most advice about failed faxes is written from how fax machines work. This page comes from how faxes actually went: 2,439 faxes that 1,382 people sent through Faxio to numbers in the United States and Canada, with the result the phone network reported for each one.

  • 83.4% arrived on the first attempt. About one fax in six did not.
  • Two thirds of failures were dropped calls, not busy lines.
  • Page count, time of day and weekends made almost no difference.
  • Most people gave up after one failure, though resending often worked.

Table of Contents

The numbers
Faxes 2,439
Different senders 1,382
Pages 8,761
Delivered on first attempt 2,033 (83.4%)
Failed 406 (16.6%)
Period September 2023 to November 2026
Destinations United States and Canada

Why faxes failed

The phone network gives a reason code when a fax does not go through. Here is how the 406 failures break down.

Reason Failures Share
Call dropped before or during the handshake 271 66.7%
Failed with no reason reported 62 15.3%
No final result ever came back from the network 41 10.1%
Line busy 25 6.2%
Number could not be reached 6 1.5%
Other 1 0.2%

The surprise is how rarely a line was busy. The usual advice for a failed fax is to wait and retry, which is right for a busy line, but busy lines were only one failure in sixteen.

The large group is the dropped call: the network connected, but the call ended before the two fax machines finished their handshake. The carrier's own documentation lists the usual causes: the number is a voice line, the receiving side hung up, or it rang for so long that the transmission timed out (SignalWire: common fax errors). In practice that means a wrong or outdated number, a machine that is switched off or out of paper, or a line that is no longer set up for fax.

Page count does not predict failure

Pages Faxes Delivered
1 1,038 82.3%
2–3 712 85.3%
4–10 516 82.4%
11 or more 173 85.0%

A longer fax keeps the line open longer, so it is natural to expect more of them to fail. They did not. A single page failed about as often as an eleven-page document, which fits the reasons above: most failures happen when the call starts, not halfway through.

Time of day and weekends

When it was sent (Eastern time) Faxes Delivered
8 am – noon 628 81.8%
Noon – 5 pm 1,056 83.7%
5 pm – 10 pm 458 84.9%
10 pm – 8 am 297 82.8%
Weekdays 2,161 83.0%
Weekends 278 86.3%

There is no time slot to avoid. Evenings and weekends were slightly better, perhaps because shared office lines are less busy, but the gaps are a few points on a few hundred faxes and could easily be chance. A machine that answers at 10 am will usually answer at 10 pm too.

Toll-free and regular numbers

Number type Faxes Delivered
Toll-free (800, 888, 877, 866, 855, 844, 833) 784 85.5%
Regular area codes 1,655 82.4%

Toll-free fax numbers did slightly better. Many of them belong to large organisations, such as the IRS and the VA, whose fax servers answer around the clock.

What happened after a failure
Failed faxes 406
Sender tried the same number again later 157 (38.7%)
…and it was delivered 61 (39% of those who tried)
Sender never tried that number again 249 (61.3%)

Most people stopped after one failure. Of those who tried again, about two in five got through. The counts for individual reasons are small, so treat them as rough guides: after a dropped call, 42 of 271 faxes later reached the same number; after a busy line, 5 of 25.

So resending is worth doing, but blind resending is not. If a fax drops twice, the number is the likely problem.

What to do with this

  1. Confirm it is a fax number. Most failures look like a voice line or a machine that does not answer. Call the number. A person, voicemail or a menu means it is not a fax line.
  2. Resend once. Two in five retries got through. If it fails again with the same reason, stop and check the number instead of sending a third time.
  3. Do not split long documents. Page count did not change the odds.
  4. Do not wait for a better time. Time of day and weekends made no clear difference.
  5. For a busy line, retry within minutes. Busy is the one failure where waiting and retrying is the whole fix. See fax not going through for the other error types.

How we measured

  • Source: Faxio's own delivery records. Each fax's result is the status the carrier reported (SignalWire for US and Canadian numbers).
  • Included: faxes to US and Canadian numbers from September 2023 to 5 November 2026 that reached a final result (delivered or failed).
  • Excluded:
    • drafts and faxes still in progress;
    • our internal test account;
    • every sender with more than 50 faxes, so that a few heavy users do not decide the averages. This removed 8 senders and 2,321 faxes, including one account that sent 497 faxes to 3 numbers in two hours.
  • International faxes are left out. Until November 2026 our carrier did not complete them, so including them would describe our setup, not the fax network.
  • "Delivered" means the carrier confirmed it. It shows the receiving machine accepted the pages, not that a person read them.
  • First attempt only. Automatic retries were added recently and touch only 34 of these faxes, so the rates above are mostly first-attempt rates.
  • Limits:
    • This is one service and one carrier.
    • Senders chose their own recipients, so the mix leans towards the offices people fax most: tax, medical, insurance and government.
    • Differences of two or three points between groups are within normal variation at these sizes.

We will update this page as more faxes come in. If you cite it, please link to this page and use the date above.