For U.S. and Canadian telephone numbers, use parentheses, not a hyphen, to separate the area code from the seven-digit phone number. For example, (123) 555–0197.

The country code for the United States and Canada is 1. Unless you are certain that a document will not be translated or distributed for use in another country, include the country code for the United States and Canada. Always include the country code when a telephone number is part of a list of numbers that includes both domestic and international numbers. For example, 1 (23) 555-0197

Use a space instead of a hyphen to separate the elements of international telephone numbers. For example, 44 (171) 555 0197

Place the area code within parentheses, unless the number is a toll-free number. For example, 0800 555 131