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.

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. Here's how they break down in local, national, and international terms.

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.

Fax number example UK international
Local fax number format for a UK number

International format

Fax number example
International fax number format for a US number

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:

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".

Fax number example UK local
International fax number format for a UK number

In the US, do I need to add a '1' before dialing a fax number?

In the US, you only need to add the '1' before dialing a fax number if you are sending a fax to a different area code.

The '1' serves as the long distance prefix. So, if you're in New York (area code 212) and you're sending a fax to Los Angeles (area code 323), you would dial 1, then the area code, and then the local number, like:

However, if you are sending a fax to a number within the same area code as you, you do not need to add the '1'. You can simply dial the local number. For instance, if you're faxing to another number in New York City, you would just dial the local number 555-1234.

How do I know if I'm looking at a fake fax number?

Verifying the legitimacy of a fax number can be a bit tricky, but there are a few steps you can take to determine if a fax number is fake:

  1. Country and area code check: Every fax number begins with a country code (for example, '1' for the U.S.) and an area code. Ensure that these codes are accurate and correspond to the correct country and region. You can look up these codes online for validation.
  2. Length of the number: Check the length of the fax number. A typical U.S. fax number will have 10 digits (excluding the country code). The length may vary for other countries, but it's usually between 10-12 digits. If the number is significantly shorter or longer, it could be a red flag.
  3. Call the number from a phone: If you suspect that the fax number might be fake, you can Test a fax line with a phone. Sometimes, fax numbers are also used as regular phone numbers, or you might hear a distinctive tone indicating that the number is for a fax machine.
  4. Send a test fax: The most effective way to verify a fax number is by sending a test fax. If the fax goes through without any errors, the number is most likely legitimate. On the other hand, if you receive an error message or the fax fails to go through, it may indicate that the fax number is fake.

Remember, however, that none of these methods, except the last, can provide a 100% guarantee. If you have serious doubts about the legitimacy of a fax number, especially in a business transaction or professional communication, it might be best to seek further confirmation from the party that gave you the number.

Note: Sometimes, when people ask about a "fake fax number" or "dummy fax number", what they really want is a random fax number that will get a response from a fax machine. If that's what you're after, we've got just the thing for you with our Fax Tester service. This service gives you a special number where you can send a test fax, receive a confirmation if the fax goes through successfully, and see the fax appear online.

How to format a fax cover sheet

The cover page is a useful addition to your fax because it contains information about how to route the document you're sending. Here's what a standard fax format includes:

  1. Your contact information: Your name, company name, and fax number.
  2. Recipient's information: The recipient's name, company name, and fax number.
  3. Date: The date you are sending the fax.
  4. Number of pages: The total number of pages including the cover sheet.
  5. Subject line: A brief explanation of what the fax pertains to.
  6. Additional notes: Any extra information or instructions that the recipient should be aware of.

The cover page helps to ensure your fax reaches the correct recipient and provides a quick overview of what to expect in the subsequent pages.

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) bitmap format. It utilizes 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.


Understanding the correct format for fax numbers, cover pages, and files is critical to ensure smooth and professional communication. Whether you're using a traditional fax machine or opting for internet faxing, this knowledge can help you avoid potential pitfalls and delays. As faxing continues to be a reliable and secure form of communication, being adept with fax formatting is an essential skill in today's business world.