Microsoft® Manual of Style, Fourth Edition

Phone numbers

For U.S. telephone numbers, use parentheses to separate the area code from the seven-digit phone number, not a hyphen. In domestic telephone lists, do not precede the area code with 1 to indicate the long distance access code. Do add 1 in international lists to indicate the country code for the United States, as described later in this topic.

Microsoft style

[phone]

[phone]

Not Microsoft style

425-555-0150

1-317-555-0123

In North America, some 800 (toll-free) phone numbers are accessible to both U.S. and Canadian callers, and some serve only one country or the other. If a number serves only one country, indicate that the number or the service it provides is not available outside that country.

Microsoft style

[phone] (Canada ...