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Format for telephone extensions

Question:

What is the correct format for writing a telephone number with an extension? Should I include the abbreviation Ext.?

Answer:

According to The Gregg Reference Manual, a comma separates the main telephone number from the extension, and the extension number is preceded by the abbreviation Ext.

Example:

  • Please contact Lisa Steward at 613-555-0415, Ext. 126 In formal correspondence, however, you may write Extension out in full.