International fax number formatter: from the letterhead to the +country form

What the fax number formatter does

The formatter turns a fax number as a person writes it into the number a fax service dials. A letterhead prints a number for the people who read it: with brackets around the area code, a leading zero for callers in the same country, dots or dashes between groups, sometimes a “(0)” to hedge between national and international readers. A fax service needs none of that. It needs the country code and the national number, digits only, in the international form, and it needs them right the first time, because a fax is a phone call and a wrong number is a call to a stranger’s line.

Type the number as it is printed, choose the country it belongs to, and the tool shows four things: the number in the +country form, the same number written for reading, the territory the number resolves to and whether Faxvio sends there, and how to dial that number from the countries people most often fax from. The normaliser that does this is the one built into the Faxvio app, so the result on this page is the result the app’s number screen would show, including the prefix rule that makes a toll-free number cost two pages per page.

What is the +country form of a fax number?

The +country form is the international public telecommunication number defined by ITU-T Recommendation E.164. It has three parts: a plus sign, which stands for “whatever access prefix your network uses to reach the world”; a country code of one to three digits, assigned by the ITU; and the national significant number, which is the area or city code followed by the subscriber number, with no trunk prefix. The whole thing is at most fifteen digits. A number written this way can be dialled from a mobile phone in any country, and it is the form every fax service, including Faxvio, stores and dials.

Why does the leading zero disappear?

In many countries a number dialled from inside the country starts with a trunk prefix, almost always a zero, that tells the exchange “what follows is an area code, not a local number”. The zero is part of dialling, not part of the number, and in the international form it is dropped: a London number printed as 020 7946 0958 becomes +44 20 7946 0958. The app’s normaliser drops one leading zero from the national number for the United Kingdom, Germany, France, the Netherlands, Japan, South Korea and Australia, whether you typed the number nationally or pasted it as “+44 020 …” with the zero left in. Spain, Denmark, Norway, the United States and Canada have no trunk prefix, so nothing is removed there; a Spanish number is nine digits from the first one.

The “(0)” convention, as in +44 (0)20 7946 0958, is a courtesy to human readers that a machine cannot use: a fax service that dials the digits as they stand reaches +44 020 …, which no exchange will route. The tool strips a bracketed zero before it does anything else, so a number copied from an email signature comes out right.

Example numbers are reserved or fictional.

Italy is the exception, and it matters

An Italian landline keeps its leading zero in the international form. Rome’s 06 1234 5678 is +39 06 1234 5678, and +39 6 1234 5678 is a different number that will not reach the same machine. Italian mobiles, which begin 3, have no zero to keep. The same rule governs Vatican City, whose numbers are reached on the Italian code with the prefix 06698, written with its zero: strip that zero and the Vatican prefix never matches, so the number resolves to Italy instead. The tool follows this rule, and so does the app; it was the app’s own normaliser that got Italy wrong until 6 September 2026, when it was corrected in all three places the rule lives.

How do I dial an international fax number from my country?

The plus sign is not a digit; it is a placeholder for the international access prefix, and that prefix depends on where you are dialling from, not on where the number is. The ITU recommends 00, and most of Europe, Africa and Asia use it. The North American Numbering Plan uses 011. Japan uses 010, Australia 0011, Hong Kong 001, and South Korea 001 or 002 depending on the carrier. Brazil is stranger still: 00 followed by a two-digit code that chooses the long-distance carrier. A mobile phone lets you skip all of this and dial the + itself. A fax app such as Faxvio dials from its carrier’s network, so the prefix is never yours to add: the app takes the +country form and the network does the rest.

Why exactly ten digits after +1, and which +1 numbers are refused

The whole of +1 is one numbering plan, the North American Numbering Plan, shared by the United States, Canada and about twenty Caribbean and Pacific territories. Every number in it is ten digits: a three-digit area code and a seven-digit local number. There is no trunk prefix; the 1 people dial first is the country code itself, which is why the tool accepts “1 415 555 0188” and “415-555-0188” as the same number. Nine or eleven digits after the country code cannot be right, and the app refuses them instead of guessing.

Because the country code does not say which territory the number is in, the area code does. The tool resolves 787 and 939 to Puerto Rico and 340 to the US Virgin Islands, both of which Faxvio sends to. Area codes belonging to the Bahamas, Barbados, Anguilla, Bermuda, the Cayman Islands, Jamaica, Trinidad and the other Caribbean and Pacific members are refused, because the carrier does not terminate there. Everything else on +1 is treated as the United States or Canada, at one page per page, unless the prefix rule below applies.

Shared dial codes: one code, several countries

+1 is not the only code shared between territories. +44 covers the United Kingdom and also Jersey, Guernsey and the Isle of Man, which the carrier treats separately: the tool resolves Jersey’s 1534 and 7797 prefixes to Jersey, which Faxvio sends to, and Guernsey’s and the Isle of Man’s to destinations it refuses. +39 is Italy and, on the 06698 prefix, Vatican City. +61 is Australia and, on 89162 and 89164, the Cocos and Christmas Islands. +7 is Russia and Kazakhstan. The normaliser matches the longest country code first, so a number beginning 358 is Finland and not something under +3, and then applies the prefix rules for that code. The destinations page draws the full resolution as a diagram.

How to read a fax number off a letterhead

Most numbers that fail to go through fail before dialling, in the reading. A short checklist:

• Keep the plus, drop everything else that is not a digit. Spaces, dots, dashes and brackets are for people. A “(0)” is a zero that must go.
• A number starting with 00 or 011 is already international. The digits after the prefix begin with the country code; do not add it again.
• A number without a country code is national. Choose the country it belongs to and let the tool add the code and remove the trunk zero.
• Check the length. Ten digits after +1, and between seven and fifteen digits in all everywhere else. A digit too few is the most common slip when a number is retyped from paper.
• Look at the prefix. An 800, 0120 or 0800 number is a service number; it works, but it uses two pages per page, and the tool says so.
• Make sure it is a fax line. Letterheads print voice and fax numbers side by side. Faxing a voice line rings a phone; nobody answers with a fax tone; the pages come back.

Which prefixes use two pages per page?

Toll-free, shared-cost and premium numbers cost the carrier more to reach than an ordinary landline, so the app charges two pages per page for them and shows that on the number screen before you send. The tool flags the same prefixes. Everything else on Faxvio’s list of 37 destinations is one page per page, whatever the country.

Bottom line

A fax number is dialled in the +country form of ITU-T E.164: a plus sign, a one- to three-digit country code and the national number without its trunk zero, at most fifteen digits. The United Kingdom, Germany, France, the Netherlands, Japan, South Korea and Australia drop a leading zero in that form; Spain, Denmark, Norway and the whole of +1 have no zero to drop, and +1 numbers are exactly ten digits. Italy is the exception that catches people out: an Italian landline keeps its 0, so Rome’s 06 1234 5678 is +39 06 1234 5678, and Vatican City is reached on the same code with the prefix 06698, zero included. The access prefix, 00 in most of the world, 011 in North America, 010 in Japan and 0011 in Australia, belongs to the caller’s network and is what the plus sign stands for. This tool applies the app’s own normaliser, resolves shared codes by prefix, flags toll-free and premium prefixes that use two pages per page, and sends nothing you type anywhere.