Table of Contents
- What is the format of a fax number?
- Do fax numbers have area codes?
- Can a fax number be 7 digits (or 6, or 8, etc.)?
- In the US, do I need to add a ‘1’ before dialing a fax number?
- Can any random number be a fax number?
- How to format a fax cover page
- What is the file format for a fax?
While many of us rely on emails and instant messaging platforms, the use of fax remains prominent in several business industries. Understanding how to format a fax, including the fax number and cover page, is an important skill to have. In this article, we’ll shed light on the format of a fax number, how to format a fax cover page, and the file format for a fax.
Looking for what fax numbers actually look like in different countries? Our companion fax number examples by country page has a quick visual reference for US, UK, Germany, Japan, Australia, Canada, and France. This page focuses on the dialing rules behind those examples, plus cover pages and file formats.
What is the format of a fax number?
When you think about fax numbers, you should know they are identical to phone numbers, and follow a specific format. This section covers the dialing rules (local, national, and international); for ready-to-copy examples in each country, see the fax number examples page.
Local format (within your city)
Locally, the fax number format is straightforward. If you are sending a fax within the same area code, you only need to use the local number. For instance, in the US, if the full number is 212-555-1234, you would simply dial 555-1234.
National format (within your country)
In the U.S., if you’re sending a fax to a different area code, you need to include the U.S. long distance prefix ‘1‘, followed by the area code and the local number. So, for the number in Alaska, you’d dial 1-907-555-1234.
In other countries, the long distance prefix is usually ‘0‘, so to fax from Paris to Lyon you would dial 04 2345 6789.
International format
For international faxing, you need to know the international access code, which is ‘011‘ in the U.S. and ‘00‘ in most other countries, then the country code, the area code, and the local number. For instance,
- If you’re faxing from the U.S. to London, UK, you would dial:
011-44-20-1234567, whereas - If you’re faxing from the UK to New York, you would dial:
001-212-555-1234.
You might see this displayed as ‘+44-20-1234567’ or ‘+1-212-555-1234’, where the ‘+‘ sign serves as a generic international access code and means “precede the number with whatever your international access code is”.
Do fax numbers have area codes?
Yes. A fax number is a phone number, so it carries the same area code as any voice line in the same place. In the US and Canada, that’s the first three digits of a 10-digit number. Outside North America, the equivalent slot is called an area code or a city code, and it sits between the country code and the local subscriber number.
If you’re sending from an online fax service, you never separate the area code out at all. Enter the whole number in E.164 international format and the platform routes it for you:
+1 555 123 4567for a US or Canadian number+44 20 7946 0000for a UK number+81 3 1234 5678for a Tokyo number
The + and country code do the work of the long-distance prefix, so there is no separate area-code step to think about. Save the fax number in that form once and it will send correctly from any online fax service, mobile app, or computer.
Two things usually trip people up on this question, and neither is really about area codes. The first is the assumption that a fax number might be a different kind of address, like an IP address or a modem ID. It isn’t – fax runs over the same voice phone network (or a modern IP replacement for it), so a fax line has the same shape as a voice line: country code, area code, subscriber. If a business gives you a fax number without an area code, they’ve handed you a partial number and you need to ask which area code it belongs to. The second is the older habit of dialing the area code as a separate step, or only when calling out of area. That’s a dialing rule for physical handsets on the copper network, not a property of the number itself – and it’s the question the dialing-1 section below covers directly.
Can a fax number be 7 digits (or 6, or 8, etc.)?
Sometimes.
A fax number can be 7 digits long, especially when you’re dialing within the same local area or city. In such instances, you do not typically need to dial the area code, which makes the effective dialing number 7 digits. This holds true in certain areas where the telecommunications infrastructure supports 7-digit dialing, such as in some regions in the United States and Canada.
However, for broader or international communications, fax numbers will require an area code or a country code, respectively, making the total number of digits more than 7.
In the US, do I need to add a ‘1’ before dialing a fax number?
It depends on how you’re sending the fax. On a traditional US landline or an office PBX still running on copper, you add the 1 before an out-of-area fax number. On an online fax service you don’t – you enter the number in international format and the service routes it. On a hosted PBX or VoIP business line (an office phone system that runs over the internet instead of copper), it’s usually optional, though a few carriers still require it.
On a traditional landline (yes)
On the copper phone network (PSTN) or a legacy PBX behind it, fax dialing follows the same long-distance rules as a voice call. The 1 serves as the long distance prefix.
If you’re in New York (area code 212) and you’re sending a fax to Los Angeles (area code 323), you dial 1, then the area code, then the local number:
1-323-555-1234.
If you’re faxing a number within your own area code, drop the 1 and just dial the 7-digit local number:
555-1234.
On an online fax service (no)
Online fax services want the number in E.164 international format – country code first, digits run together, no spaces or dashes required – without a bare leading 1:
+1 555 123 4567for a US number+44 20 7946 0000for a UK number
The service reformats the number before sending, so a stray 1 on a US number is absorbed either way. Save the number in +1 form once and it will send correctly from a mobile app or a computer.
On a hosted PBX or VoIP line (it depends)
Hosted PBX, VoIP business lines, and analog terminal adapters (small boxes that connect a physical fax machine to an internet phone line) fall somewhere in between. Some carriers keep the old rule of prefixing 1 for out-of-area calls; others accept a bare 10-digit number or the full +1 form. The wrong format usually returns a fast-busy tone (the rapid on-off signal that means the call didn’t connect) or a routing failure, rather than reaching a wrong number.
If a specific fax keeps failing on a hosted line, try each of the three formats in turn: with 1, without 1, and as +1XXXXXXXXXX. Note which one gets through, then save that format in the machine’s speed-dial.
How to tell which situation you’re in
A quick self-check. If you dial from a physical handset with a wall jack and no computer in the loop, that’s a traditional line and out-of-area faxes need the 1. If you send through a web page, a phone app, or an email-to-fax address, that’s an online fax service and E.164 without the 1 is right. If you have a fax machine plugged into a small adapter or an office VoIP handset, try both formats on a number you know works – the carrier’s response will tell you which one it wants. If you’re still not sure, ask whoever installed the line; the service ticket or the PBX admin will know without you having to test-fax an unrelated number.
Can any random number be a fax number?
No, a random phone number will not necessarily serve as a fax number. There are some criteria that a number must meet to be a valid fax number:
- Length of the number: The length of the number should conform to the local telecommunications regulations. For instance, in the United States, a fax number without the country code typically includes an area code and a 7-digit local number, for a total of 10 digits.
- Assignment and activation: A number must be assigned by a telecommunications provider and activated as a phone line.
- Proper formatting: Fax numbers must also adhere to the proper format, which usually includes a country code (for international faxes), an area code, and a local number.
- Availability: The number cannot already be in use as a phone line unless it is specifically set up to handle both voice calls and faxes, which some modern systems can handle.
In essence, while a random number could potentially be a fax number, it would have to meet these criteria. Simply choosing a random number and attempting to send a fax to it is unlikely to be successful unless that number is a valid, active fax line.
How to format a fax cover page
The cover page is where you tell the recipient what’s in your fax and who it’s for. For the essential fields, formatting tips, common pitfalls, and downloadable US Letter and A4 templates, see the dedicated fax cover page guide.
What is the file format for a fax?
Traditional fax machines operate by transmitting data via a phone line, scanning the document and converting it into a bitmap image. This bitmap is then sent through the phone line where the receiving fax machine will print the bitmap image.
TIFF Group 3 (.tif)
The most common file format is TIFF (Tagged Image File Format) because of its high quality and excellent compatibility with fax machines. However, the variant of TIFF often used in faxing is known as TIFF Group 3 or TIFF G3.
TIFF G3 is a monochrome (black and white) image format. It uses a compression technique that is very efficient for documents containing mostly text. One notable feature of this format is its ability to store multiple pages within a single TIFF file, making it ideal for multi-page faxes. Because of these advantages, the TIFF G3 format has become a standard in the world of faxing, both for traditional and digital faxes.
PDF is also great
While the TIFF G3 format is a standard in traditional faxing, the Portable Document Format (PDF) has become a popular choice for online fax services. PDFs maintain the formatting and layout of a document regardless of the device or software used to open them, making them ideal for online faxing.
The PDF format is universally compatible and is designed to preserve the original appearance of a document, including its page size, fonts, images, and layout. This is especially valuable in a professional setting where it’s crucial to maintain the clarity and integrity of documents being transmitted.
But others, too
Now in the modern era of digital or internet faxing, fax services have expanded their file format acceptability. Now, alongside TIFF and PDF, formats such as DOC, DOCX, JPG, and PNG are also accepted. These digital files are usually converted into a fax-compatible format like TIFF G3 in the background by the service.