A fax number is a telephone number used to send documents electronically. It usually consists of 10 digits, although some countries may have different formats. This discussion will focus on the different formats of fax numbers and what is the most common format.We will discuss the different formats of fax numbers, such as the number of digits, the different types of numbers used, and what is the most common format. We will also discuss the advantages and disadvantages of each format, as well as how to ensure you are using the right format for your fax number.