Teams does not currently provide a way to change the length of the Internal Extensions. However, there is a workaround for the customers to achieve this via the Microsoft Team Admin Center. The summary is to duplicate the normalization rule within the Global dial paln and then modify the duplicate to match longer numbers.

Start by logging in to your Office 365 Admin Portal and Select Teams Admin Center, then on the Left Navigation go to Voice 






  • Dial Plan > Click Global. You should now see the normalization rules. We creates a rule that allows feature codes (dialed numbers that start with an * or #) and short numbers to be passed through as-is to the far end. Short numbers are considered extension numbers and so we match them with a rule to avoid Teams converting these to E164.
  • Click Add by the normalization rules table. Enter a suitable name and description, perhaps mentioning that the purpose is to match larger extension numbers.

  • Selected 'Advanced' to allow use of a regex.
    • The 'If' condition by default is: ^([\*\#][\*\#\d]+|[1-9]\d{0,5})$
    • If you are unfamiliar with regular expressions the important number is the 5 near the end. Increase this to 6 if you want to match 7 digit extensions (note we assume extensions start with an explicit 1-9, which is why this is one less than the total number length). For example: ^([\*\#][\*\#\d]+|[1-9]\d{0,6})$
    • The 'to' condition should be $1
  • The existing normalization rule should be left untouched. Ensure your new rule is above it on the global dial plan, .e.g below you can see new Normalization rule is created as “My Company rule” and the dial plan is set for the Teams users to dial number maximum of 7 digits



Note: It's important that the original rule is left untouched, as this will be checked by our sync and amended if different from the expected default.