# Fax Not Going Through? What FaxUp's Failed Faxes Show The real reasons faxes fail, from FaxUp's own delivery records: dropped calls, no fax tone, busy lines. What each one means, how FaxUp retries, and what you can fix. By [Dan Bayer](https://faxup.net/about) · Last updated: November 12, 2026 **Most faxes fail because the call drops partway through, nothing answers with a fax tone, or the line is busy; check that the number is really a fax line, send during office hours, and split very long or dark documents.** In FaxUp's records, 88.4% of faxes were delivered, and about half of the faxes that hit a problem were rescued by an automatic retry. A fax is a phone call between two machines, so it fails for phone-call reasons: nobody answers, the line is busy, the call drops. We looked at every fax sent through FaxUp from February 2024 to November 10, 2026 to see which of those actually happen, and what helps. ## The numbers Of 1,666 faxes that reached a final result, **1,473 were delivered (88.4%)** and **193 failed** after all retries. Retries matter: of the 1,564 faxes with a carrier status log, 288 ran into a busy line, no answer or a failed attempt along the way, and 153 of those were still delivered on a later attempt. More numbers, including how long delivery takes, are in [fax delivery statistics](https://faxup.net/fax-statistics). Counts here are totals only, with no personal data. For the 193 failed faxes, the carrier logs give these reasons. A fax can show more than one across its retries, so the counts overlap: | What the carrier reported | Failed faxes with this reason | What it usually means | | --- | --: | --- | | The call dropped partway through | 59 | The connection broke during the pages | | Timed out waiting for the first fax signal | 36 | Something answered, but not a fax machine | | Call failed (no detail given) | 56 | The call didn't connect or ended early | | Busy | 15 | The fax line was in use | | Couldn't agree a speed with the other machine | 3 | The two machines' modems couldn't match | | No answer, other errors | 4 | No pickup, or the machine stopped replying | Another 27 faxes never got a final report from the carrier and were closed as failed by our own check after 24 hours (with the credit returned), and 42 have no reason recorded. ## What each failure means, and what to do ### The call dropped partway through The two machines started talking (the handshake defined in ITU-T T.30) and then lost each other mid-document. It is more likely on long documents, pages with large black areas, and long-distance or noisy lines. - Send it again later; a different call often gets through. - Split a long document into two faxes. - Lighten heavy pages: a dark photo or a scanned page with a grey background takes far longer to send. The [fax preview](https://faxup.net/fax-preview) flags dark areas. ### No fax signal: something answered, but not a fax The call connected, but no fax machine answered with fax tones. This is what happens when the number is a voice line, a voicemail box, or a fax machine that is switched off and forwards to voice. - Check the number against the letter or form. Many offices list phone and fax side by side. - Call the number from your phone. If a person or a recording answers, ask for the fax number. - If it's an office, send during their working hours. Abroad, check the time difference; see [faxing Australia](https://faxup.net/fax-to-australia) for an example. ### Busy The line was in use when the call was placed. FaxUp retries automatically, waiting longer each time. In our records, 51 faxes hit a busy line at least once and 36 of them (71%) were delivered on a later attempt. ### The machines couldn't agree a speed Rare: 3 faxes in our records. The receiving machine and the carrier couldn't find a modem speed both support. FaxUp's later retries use standard resolution. If it still fails, the receiving machine may need attention; tell the recipient. ## How FaxUp handles a failure for you 1. **Retries:** up to 5 more attempts after the first, 15, 30, 45, 60 and 75 minutes apart. That is close to four hours in total, so a fax that shows "Sending" for a while is often just waiting for its next try. 2. **Lighter retries:** from the second retry, pages go at standard resolution (about half the vertical detail of fine mode), which is quicker to send over a weak line. 3. **Credit back:** if every attempt fails, the fax is marked failed and its credit returns to your balance. 4. **Refusals before sending:** mobile and premium-rate numbers, and countries we can't reach, are refused before dialling, with nothing charged. ## A checklist before you resend - Is it a fax number? Not a mobile, not the main phone line. - Is the country right in the picker, and the leading 0 dropped for numbers abroad? - Will the machine be on? Office hours, their time zone. - Is the document easy to send? No full-page dark photos, no tiny text, and long documents split if they keep dropping. When it does go through, keep the [transmission report](https://faxup.net/fax-confirmation) as your proof. Ready to send it? One fax is $2.99, any number of pages, with no subscription. You see every page as it will print before it goes, and a fax that can't be delivered gives its credit back. [Try the fax again](https://faxup.net/send)[Fax preview (free) →](https://faxup.net/fax-preview) Find pages that are slow or hard to send: dark areas, tiny text, content at the edges. ## Questions ### Why does my fax keep failing? In FaxUp's records the most common causes are a call that drops partway through, and a number where no fax machine answers. Check that the number is a fax line (not a phone or voicemail), send at a time the office is open, and split very long or dark documents. ### Do I pay for a fax that failed? No. FaxUp retries the call on its own, and if the fax still isn't delivered, the credit goes back to your balance. ### How many times does FaxUp retry? Up to 5 times, waiting longer before each attempt: 15 minutes, then 30, 45, 60 and 75. From the second retry on, the fax is sent at standard resolution, which is quicker over a poor line. ### What does 'busy' mean on a fax? The fax line was in use when we called. FaxUp retries automatically with longer waits in between, so a busy line on the first try often gets through on a later one. ### The status says sending for a long time. Is it stuck? Usually it is waiting for a retry, which can take a few hours in total. If our carrier never reports a result, the fax is marked failed after 24 hours and the credit is returned. ### My number was refused before sending. Why? FaxUp refuses numbers that can't receive a fax, such as mobile and premium-rate ranges, and countries it can't reach yet. Nothing is charged in that case. Check the country in the picker and that the number is a fax line. ## Related guides - [Fax confirmation and proof of deliveryWhat a fax transmission report shows, how to get FaxUp's delivery report PDF on your iPhone or Android phone, and what it does and doesn't prove when an office says it never got your fax.](https://faxup.net/fax-confirmation) - [One fax, no subscriptionPay $2.99 for a single fax of any length, from the web or the FaxUp app, with nothing that renews. When a credit pack or a plan is cheaper, worked out with real FaxUp prices.](https://faxup.net/one-fax-no-subscription) - [Fax to AustraliaWrite an Australian fax number the right way (+61, no leading 0), pick a good time across Australia's time zones, and send it from your browser for $2.99 a fax.](https://faxup.net/fax-to-australia) - [Fax a photo from an iPhoneFax a picture of a document, a receipt or a screenshot straight from iPhone Photos, HEIC included. How each photo becomes a fax page and how to make it readable in black and white.](https://faxup.net/fax-photo-from-iphone) ## Sources - FaxUp delivery records: aggregate counts of faxes with a final status, February 20, 2024 to November 10, 2026, read November 12, 2026 (no personal data) - [ITU-T Recommendation T.30: procedures for document facsimile transmission (the handshake between fax machines)](https://www.itu.int/rec/T-REC-T.30) - [ITU-T Recommendation T.4: Group 3 facsimile (standard and fine resolution)](https://www.itu.int/rec/T-REC-T.4) - [FaxUp pricing and refund of failed faxes](https://faxup.net/pricing) Outside sources were checked on November 12, 2026. Something wrong or out of date? Email [support@faxup.net](mailto:support@faxup.net). --- Source: https://faxup.net/fax-failed (Markdown copy of the page; the HTML page is canonical).