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Mark Brezicky / /

Skype for Business Online Telephone Numbers and Porting FAQ

How many telephone numbers can I obtain from Microsoft?

There are three different types of phone numbers in Microsoft Phone system: User, Service, and Toll-Free.  Each has their own formula for the maximum amount that you can have.

 User Numbers

The number of phone numbers is equal to the total number of Domestic Calling Plan and/or Domestic and International Calling Plan licenses multiplied by 1.1 + 10 additional phone numbers (n x 1.1 +10)

Example: 100 Domestic Calling Plan licenses allows for 120 phone numbers (100 x 1.1 +10 = 120.0 120)

Service and Toll-Free Numbers

Microsoft allots a specific maximum amount of telephone numbers based on the total number of Phone System and Audio Conferencing licenses.

If there are 1-25 licenses then 5 telephone numbers are given.

If there are 26-49 licenses then 10 telephone numbers are given.

If there are 50-99 licenses then 20 telephone numbers are given.

If there are 100-149 licenses then 30 telephone numbers are given.

If there are 150-199 licenses then 40 telephone numbers are given.

If there are 200-499 licenses then 65 telephone numbers are given.

If there are 500-749 licenses then 90 telephone numbers are given.

If there are 750-999 licenses then 110 telephone numbers are given.

If there are 1,000-1,249 licenses then 125 telephone numbers are given.

If there are 1,250-1,499 licenses then 135 telephone numbers are given.

If there are 1,500-1,999 licenses then 160 telephone numbers are given.

If there are 2,000-2,999 licenses then 210 telephone numbers are given.

If there are 3,000-6,999 licenses then 420 telephone numbers are given.

If there are 7,000-9,999 licenses then 500 telephone numbers are given.

If there are 10,000-14,999 licenses then 600 telephone numbers are given.

If there are 15,000-19,999 licenses then 700 telephone numbers are given.

If there are 20,000-49,999 licenses then 1000 telephone numbers are given.

If there are 50,000+ licenses then 1500 telephone numbers are given.


More information regarding the amount of telephone numbers you can get can be found here:

Can I request specific telephone numbers?

If specific numbers are not listed in the Skype for Business Admin center you can fill out a form for new user and service numbers to obtain new numbers (links below).  This can also be used to attempt to obtain consecutive blocks of numbers.

 User Number form:

Send to

 Service Number form:

Complete and send to

How much am I charged per telephone number?

In traditional SIP Trunk and PRI setups, customers are typically charged for Direct Inward Dial (DID) numbers they had on their circuit, even those not used.  In Microsoft Phone System, there are no additional charges for the DIDs that are assigned to your tenant.  They are accounted for in the Phone System, Audio Conferencing, and Domestic/International Calling plan licenses.

How many numbers can you port into Microsoft Phone System?

The limits above don't include phone numbers you have ported or transferred to Microsoft.  You can theoretically port as many numbers as you want or have into Microsoft Phone System.

How can I obtain additional numbers?

If you have enough licenses you can use the Skype for Business Online Admin Center or PowerShell to obtain new User, Service, or Toll-Free numbers.  You can easily determine the current amount of available telephone numbers that you can acquire by reviewing the

Voice > Phone Numbers tab in Skype for Business Online Admin Center or running the PowerShell cmdlet


Additional licenses would be required if new numbers are required once your limits are reached.  If you have unused numbers they can be selected and deleted.  This will allow you to obtain numbers in another region. 

Note: Numbers ported in DO NOT count towards the maximum limit of numbers you can obtain from Microsoft.

How do I convert a User number to a Service number?

If you port a number over as a User number that was meant to be a Service number you need to send your PIN and the list of user numbers you want to convert to service numbers to

To set your PIN, use Skype for Business Online Admin Center

Voice > Port order tab and select Set up and manage the PIN. 

Your PIN needs to contain 6-10 digits (numbers only). 

What information is required to port my numbers to Skype for Business Online?

If you are porting under 999 numbers from the same carrier and account, you can use the Skype for Business Online Admin Center to create your port order.  You need to provide the following information:

  • Account Number
  • Billing Telephone number (BTN)
    • If not doing a full port, you must not include the BTN in the port
  • PIN (If required by carrier)
  • Company Name
  • Authorizing Person
  • Service Address
  • List of numbers in E.164 format
  • Full or Partial Port

You need to submit a manual request for the following scenarios:

  • Transferring more than 999 numbers
  • Transferring Service and/or Toll-Free numbers
  • Port orders where Additional assistance is required


If you are comfortable with the online wizard and have all the required information, the process is fairly automatic, and you will get email notifications of any approvals or issues along the way.  For manual requests, you can open a support ticket or email Microsoft's porting team directly at for further assistance and guidance.  Manual requests require a Letter of Authorization to be completed per request.


Letter of Authorization (LOA) for the U.S. (user and service numbers) (v.3.1)(en-us)
Letter of Authorization (LOA) for the U.S. (toll free numbers) (v.3.2)(en-us)


Do I have to port all numbers at once?

No.  You can do as a partial port for as little as a single number.  However, you cannot port the BTN if not doing a full transfer.


When does Microsoft schedule number ports?

Porting can be scheduled ONLY on business days (Mon to Fri; between 8 am to 7 pm EST).  Toll-Free numbers can be ported only at 11:30 AM EST on business days.  Microsoft currently does not do any porting on weekends or holidays.


The online wizard only allows you to select times between 9 am and 3 pm EST.  Times outside that window require a manual request.


How long with the porting process take?

Typically, small ports can be completed in about 7-14 days.  Some larger ports can take up to 30 days.  In most cases there are two reasons for delays.  First is due to inaccurate information provided to Microsoft regarding your current account.  Second is due to delays from the losing carrier.  Typically, the losing carrier will be professional and not do anything to prevent or prohibit the transfer, but there are some cases where the losing carrier may do something to cause a delay in the port.  As they are the losing carrier they are not always highly motivated to assist with your request.


Can you port numbers from Microsoft to another provider?

Yes, but you are required to set a PIN and this PIN will be required to port out numbers from Microsoft.  To set your PIN, use Skype for Business Online Admin Center


Voice > Port order tab and select Set up and manage the PIN. 


Your PIN needs to contain 6-10 digits (numbers only).  This PIN must be provided to the other carrier for their request.


Any number that was originally ported to Microsoft can be freely ported out at any time.  Numbers that you have obtained from Microsoft may not be capable of porting to another service provider.  This is to prevent customers from obtaining a great deal of numbers and immediately porting them out.


Best practices for handling large, multi-site ports

  • Maintain current carrier accounts in good standings until all numbers are ported.


  • Create a small, pilot group of numbers to port over to Microsoft at least several weeks prior to production port. This will validate activities that are required post-port as well as verify accurate information was provided to approve and complete the port order.


  • A unique request is required for each carrier and type of number provided. User, Service, and Toll-Free numbers cannot be ported together.
    • The User/Service DIDs can be ported in on a single request provided, all of them are on the same account with your current carrier, associated with the same service address, tagged to the same Billing Telephone Number (BTN)


  • Communicate with Microsoft's Porting Team ( for coordination assistance. They can provide a template spreadsheet to allow you to consolidate all porting requests and sites as well as create the port requests for you.
    • If working with Microsoft’s porting team, provide them as much information and documents as possible, including copy of latest bill and/or Customer Service Records (CSR).  This can help Microsoft root out unknown variables that may delay your port orders.


  • Once port orders are approved for transfer, all the telephone numbers are available for assignment in Skype for Business Online. This allows you to provision users in advance of the port to minimize downtime.


  • Ensure that you have Communication Credits available in your tenant if you wish to port Toll-Free numbers.


  • Auto Attendants and Call Queues can be setup in advance of the port. Temporary numbers can be assigned to test and validate their functionality prior to the port.  Once their actual numbers get ported, simply change the number.


A porting process can be very complex and confusing.  With over 1300 Unified Communication projects and 4-time Microsoft UC Partner of the Year, Enabling Technologies has been involved in many number porting processes from a variety of carriers.  Microsoft is making strides to make this process less complicated and easy for customers to complete without issues.  Together, we can work with you to make your vision of moving Voice to the cloud a reality.  To see more of what Enabling Technologies can offer see the Move IT to the Cloud section of our website.

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