International fax number: the format that works

Short answer: the vast majority of international faxes that "won't go through" fail before the dial tone, for an absurdly typographical reason: the number was copied exactly as printed on the recipient's letterhead, that is, in the national format of the destination country. From France, you dial 00 + country code + the number without its leading zero (00 49 30 … for Berlin, 00 32 2 … for Brussels, 00 39 06 … for Rome — Italy, for its part, keeps its zero). From Quebec and the rest of Canada, the international prefix is not 00 but 011 (011 33 1 … for Paris), and a Canadian number is dialled as 1 + ten digits. An online fax service, meanwhile, almost always expects the E.164 format: + or 00, country code, national number without the trunk prefix, no spaces, dots, dashes or brackets. Three digits in the wrong place, and the transmission report shows "invalid number", "no answer" or, worse, a voice answering at the home of someone who has never owned a fax machine.

About MondialFax. This article is an informational guide, with no connection to any telecom operator, government body or official directory. MondialFax sends faxes free of charge and without registration to seven destinations (France, Belgium, Germany, Spain, Italy, Portugal, Canada) from a browser, with a daily sending limit. It does not assign a number and does not handle incoming faxes. See the supported countries page and the country code directory.

Three notations for a single number

The same German fax machine can be written three perfectly correct ways, depending on who is writing it and from where:

The + in the international notation is not a digit: it is a convention meaning "insert here the exit prefix of the country you are calling from". In France, Belgium, Germany, Spain, Italy and Portugal, that prefix is 00 (a standard harmonised across Europe following the work of the ITU and CEPT). In Canada and the United States, it is 011. Hence the rule that solves 80% of failures: + = 00 in Europe, + = 011 in Canada.

The second habit to acquire is symmetrical: when you switch from national to international, the leading zero (the trunk prefix) disappears. 030 in Berlin becomes 30; 02 in Brussels becomes 2; 91 in Madrid never had a zero; 01 in Paris becomes 1. The famous exception is Italy, which folded the zero into its geographic numbers with the 1998 reform: you really do dial 00 39 06 for Rome, and dropping the zero makes the call fail.

Country by country, seen from France or Quebec

The seven destinations served, with the format you actually need to dial.

Germany — 00 49

German Vorwahlen (area codes) vary widely in length (30 Berlin, 89 Munich, 69 Frankfurt, 221 Cologne, but also five-digit codes in rural areas) and subscriber numbers follow no standard length: a German fax number can run anywhere from six to eleven digits after the area code. You always drop the leading zero. Many German organisations also display their number as +49 (0)30 …: the brackets mean precisely "keep this zero when dialling from within Germany, discard it from abroad". As for recipients, a German lawyer will redirect you to beA, a medical practice to KIM, but Steuerberater (tax advisers), notaries, property managers and industrial SMEs still publish a Faxnummer (fax number). A real-life detail: if you are copying these numbers out by hand from a stack of letters, a chisel-tip highlighter saves you from reading the same line three times over.

Belgium — 00 32

A short, readable format: a one- or two-digit area code (2 Brussels, 3 Antwerp, 4 Liège, 9 Ghent, 71 Charleroi, 81 Namur), then six or seven digits. From France: 00 32 2 123 45 67. Belgian mobiles (47x, 48x, 49x) do not receive faxes. The federal administration is pushing eBox and MyMinfin, but municipalities, health insurance funds and notaries still keep a number. A useful detail: Belgium has entirely abandoned national notation without the zero, which cuts down on ambiguity.

Spain — 00 34

Spain has no trunk zero. Numbers are nine digits long, province code included (91 Madrid, 93 Barcelona, 96 Valencia, 95 Seville, 981 A Coruña), and you dial them in full: 00 34 91 123 45 67. This is the country where the most common mistake is adding a zero out of habit from the French format. Public bodies will point you to the registro electrónico (electronic registry) and Cl@ve; what remains are gestorías (administrative agencies), private clinics, hotels and building management companies.

Italy — 00 39

The opposite case: the zero stays. 00 39 06 for Rome, 00 39 02 for Milan, 00 39 081 for Naples, 00 39 055 for Florence. Italian mobiles (3xx) never carry a zero. Italy has moved massively to PEC, but law and accountancy firms (studi of lawyers and commercialisti, chartered accountants), private clinics and building management offices still keep a fax.

Portugal — 00 351

Nine digits, no trunk zero: 21 Lisbon, 22 Porto, 289 the Algarve, 291 Madeira. So 00 351 21 123 45 67. Mobiles start with 9. The Finanças (tax authority), Segurança Social (social security) and CTT point you to their portals, but firms, clinics and condomínios (homeowners' associations) still answer.

Canada — 00 1 from Europe, 1 from within Canada

Canada shares the North American Numbering Plan with the United States: a three-digit area code + seven digits, ten digits in all, never with a zero. From France: 00 1 + the ten digits. From Montreal to Quebec City: 1 418 … (ten-digit dialling has been mandatory in Quebec since the arrival of overlay area codes). The useful codes: 514 and 438 for Montreal, 450 and 579 for the surrounding belt, 418, 581 and 367 for Quebec City, the Lower St. Lawrence and the Gaspé, 819 and 873 for the Outaouais, the Laurentians and Abitibi, 613 and 343 for Ottawa, 416/647/437 for Toronto, 604 for Vancouver, 902 for Nova Scotia and Prince Edward Island. Watch out for the reverse trap: a number written 1-800-… is a toll-free number, often unreachable from abroad — for an international fax, always look for the ten-digit geographic number published alongside it.

France — 00 33 from Europe, 011 33 from Quebec

Drop the zero: Paris 1, Lille 3, Lyon 4, Marseille 4, Bordeaux and Toulouse 5, Nantes and Rennes 2. So from Montreal, a fax to a Paris office is dialled 011 33 1 … and not 011 33 01 …. French numbers starting with 09 (VoIP) and the older 08 ones pose a different problem: many 08 numbers are premium-rate services that are not reachable from abroad.

What an online fax form expects

A physical machine dials literally what you type, in order, sometimes with a switchboard exit prefix (0 or 9) to add in front — a point covered in detail by our guide on routing a fax number behind a switchboard. An online service, by contrast, normalises: it expects an E.164 number and rejects anything that looks like human formatting.

Rules that prevent rejections:

• No spaces, dots, dashes, slashes or brackets.
• One international prefix only: either + or 00, never +00.
• No Fax:, no Tel./Fax, no "ext. 212" accidentally copied along.
• No extension: a fax cannot navigate an interactive voice response system. If the letterhead shows an extension, that is a phone number, not a fax number.
• Check the total length: an E.164 number never exceeds fifteen digits, country code included. An eighteen-digit German number means a zero or an area code has been counted twice.
• Strip out invisible characters pasted from a PDF (non-breaking spaces, em dashes): they are the silent cause of half the "invalid number" errors after a copy-paste.

A practical tip for batches of faxes: copy the numbers out once and for all in international format into a telephone address book, or into a spreadsheet, rather than rereading the correspondent's letterhead every time. That way, mistakes only happen once.

How to read a foreign number written any which way

Four common notations, and what they translate to when actually dialling from France:

And two warning signs to check before sending:

• A single number for "Tel./Fax": the line is shared, and the machine may be in telephone mode. Sending outside office hours stands a better chance of getting through — a topic covered in our article on the time difference between Quebec and Europe.
• A number published before 2020 on a PDF that has never been updated: with the copper switch-off in Germany, Spain and Portugal, many fax lines were cancelled rather than migrated. The point is covered in detail in The copper switch-off outside France: your faxes country by country.

When the format is right and it still fails

A correct format is no guarantee of delivery. The remaining causes, in order of frequency:

1. The line no longer exists. A fax to a cancelled number returns "no answer" or an unavailable tone, not "invalid number".
2. The recipient has moved to a digital channel. PEC in Italy, beA and KIM in Germany, eBox in Belgium, the registro electrónico (electronic registry) in Spain, the Revenu Québec and CRA portals in Canada. The number is still on the website, but the inbox is switched off.
3. T.38 negotiation fails on the recipient's carrier side: the page goes out, but the document arrives truncated or unreadable. Our guides on T.38 over VoIP and on sending failures cover this point.
4. The source document is poor. A creased or stapled original feeds badly: a rigid document folder to carry the pages and a manual paper trimmer to cut a slip cleanly are worth more than a page pieced back together with sticky tape. On the scanning side, a portable sheet-fed scanner gives far better results than a photo taken handheld with a phone.

Key takeaways

• + means "exit prefix": 00 from Europe, 011 from Canada.
• Drop the national zero everywhere, except in Italy where it is part of the number; Spain, Portugal and Canada never had one.
• Country codes to remember: France 33, Belgium 32, Germany 49, Spain 34, Italy 39, Portugal 351, Canada 1.
• A Canadian number is dialled in full, all ten digits; toll-free 1-8xx numbers are often unreachable from abroad.
• An online form wants pure E.164: digits only, fifteen at most, no extension and no formatting.
• Mobiles do not receive faxes: check the prefixes (3xx in Italy, 6/7 in Spain, 9 in Portugal, 47x-49x in Belgium, 15x-17x in Germany).
• Correct format but persistent failure = a cancelled line or a digital channel adopted by the recipient: confirm by email or phone at that point.

To test a format before an important transmission, the sending a fax abroad page and the country code directory give the details for each destination; the sending form accepts international notation directly.