How can caller ID be used in your organization

Caller ID consists of two user-facing pieces of information:

  • A phone number (referred to as CLID or calling line ID). This is the Public Switched Telephone Network (PSTN) number presented as the identification of the caller.

  • A Calling party name (typically referred to as CNAM).

The caller ID functionality is available to all Phone System users regardless of PSTN connectivity option: Microsoft Calling Plan, Operator Connect, or Direct Routing.

You can control Caller ID for both inbound and outbound calls by using a policy called CallingLineIdentity. For more information, see More about Calling Line ID and Calling Party Name.

Outbound PSTN caller ID

For the outbound PSTN caller ID, the following options are available.

  • The telephone number assigned to the user, which is the default.

  • Anonymous, which is available by removing the presentation of the user’s PSTN number.

  • A substitute phone number, which can be:

    • A telephone number that is classified as a service and toll-free number in your Calling Plans telephone number inventory. It is assigned to a Teams Auto Attendant or Call Queue.

    • A telephone number through Operator Connect or Direct Routing that is assigned to a resource account used by a Teams Auto Attendant or Call Queue.

  • The Calling Party Name or CNAM set on the outbound PSTN call.

For more information, see Create and manage Caller ID for users.

End user control of outbound caller ID

Users can change their caller ID setting to Anonymous by setting the EnableUserOverride attribute.

If the outbound caller ID is set to Anonymous, the EnableUserOverride has no effect, and the caller ID is always set to Anonymous. The default value of EnableUserOverride is False.

Your end users can set their caller ID to Anonymous by going to Settings > Calls, and then under Caller ID, select Hide my phone number and profile information for all calls. It takes a few minutes for this setting change to reflect on new calls.


Keep the following in mind:

  • You can't assign the following types of phone numbers for the outbound caller ID:

    • Any phone numbers that are classified as a user in your Calling Plans telephone number inventory.

    • Any on-premises telephone number via Direct Routing that is assigned to a user.

    • A Skype for Business Server on-premises telephone number.

  • The use of resource account phone number substitution works for Teams users. The substitution of service phone number works for Teams users.

  • Calling Party Name is sent on calls where the caller ID is substituted with LineUri, a service or resource account phone number, and when the caller is a Teams user.

  • Calling Party Name can have a maximum of 200 characters, but downstream systems might support fewer characters.

  • For Direct Routing, the phone number substitution and the Calling Party Name is sent in the FROM SIP header. If the corresponding OnlinePstnGateway is configured with ForwardPai = True, the P-ASSERTED-IDENTITY SIP header will contain the real calling user.

  • EnableUserOverride has precedence over other settings in the policy--unless substitution is set to Anonymous. For example, assume policy instance has substitution using a resource account and EnableUserOverride is set and enabled by the user. In this case, the outbound caller ID will be blocked and Anonymous will be used. If a policy instance has substitution set to Anonymous and EnableUserOverride is set, then the outbound caller ID will always be Anonymous, regardless of the end user setting.

Inbound caller ID

Phone System shows the incoming external phone number as the caller ID. If the number is associated with a user or contact in Azure AD or a personal contact, the Skype for Business and Teams clients will show the caller ID based on that information. If the phone number is not in Azure AD or a personal contact, the telco-provided display name will be shown if it is available.

The BlockIncomingCallerID attribute allows for blocking the caller ID on incoming PSTN calls. You can set this attribute, but it isn't available to your end users on the user settings page. When this setting is enabled, the incoming PSTN caller is displayed as coming from Anonymous.

To block the inbound caller ID, see Set the Caller ID for a user.

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