They range from the largest long-distance carriers to local independent bureaus. Differences among providers more often concern pricing than issues of service, since their offering tend to be quite similar. In order to compare pricing, you will need to have a sense for your expected use. This requires understanding how often you will use the service, the average length of a fax, the number of recipients, and the frequency with which the recipient list will be updated. These numbers can then be used to compare services.
Services structure their charges in several different ways.
Most base their charges either on the number of characters sent, the number of pages sent, or the total transmission time for the document. To compare rates, you can usually assume that there are about 2,500 characters per page of text, with a single page taking about 45 seconds to send. Keep in mind that graphics can slow transmission considerably, and that additional pages will require about 30 seconds apiece. The most economical services offer rates that can be as low as 25 cents a minute during peak hours and 19 cents a minute during off-peak hours. Sometimes, services add surcharges to the basic fax transmission fees.