What it does

Puts a phone number and conference ID on Teams meeting invites so people can join by phone, and lets people in a meeting call a phone number out into it. Microsoft runs the conferencing bridge; you supply licences and decide which numbers appear on invites.

Key facts

• Licences are needed only for people who schedule or lead meetings that need dial-in. People who dial in need no licence or setup.
• Audio Conferencing is included in Microsoft 365 E5 and Office 365 E5, and is an add-on for other plans such as Business Standard, E1 and E3. With the Teams unbundling, check what the tenant's own suite/Teams Enterprise SKUs carry rather than assuming.
• Audio Conferencing doesn't need a Teams Phone licence.
• Shared numbers are assigned automatically when the organisation is enabled, can be shared with other Microsoft 365 organisations, and their language settings can't be customised. Venezuela, Indonesia and the UAE don't get an automatic toll number.
• Dedicated numbers belong to your organisation and can have custom languages. Get them through the Teams admin center, by porting, or by Microsoft's request form. They can be toll or toll-free, availability varying by country/region.
• Communications Credits are required for toll-free bridge numbers and for dial-out to international numbers. Microsoft recommends assigning the Communications Credits licence (no cost) to the same users as Audio Conferencing.
• Bridge settings cover default and alternate languages, entry/exit notifications and PIN length. Numbers can take up to 24 hours to appear on invites.
• Dial-out from meetings is restricted per user (or tenant-wide) with the dial-out policy: Grant-CsDialoutPolicy -Identity <user> -PolicyName <policy> or -Global. View the options with Get-CsOnlineDialOutPolicy.
• Policy instances combine conference and user-PSTN restrictions, for example DialoutCPCandPSTNInternational, DialoutCPCDomesticPSTNInternational, DialoutCPCDisabledPSTNInternational and Zone A variants such as DialoutCPCZoneAPSTNDomestic.
• "Domestic" for meeting dial-out means the same country/region as the organiser's Microsoft 365 location, not the caller's.
• Webinars and town halls don't support attendee dial-in; external presenters can't dial in to events either.

When to use / skip

Use it wherever people still join from phones — field staff, drivers, external parties on poor connections, and boards who insist on a phone line. Most enterprises need it for at least their regular external-facing organisers, and it's in E5 anyway.

Don't license everyone by default on non-E5 tenants just because. Look at who actually hosts meetings with external or mobile participants. Equally, don't skip it for executive assistants who schedule on behalf of execs — the organiser's licence is what puts the number on the invite.

If the client wants dial-out mainly so attendees can say "call me", that's dial-out from the meeting and it's governed by the dial-out policy and Communications Credits, not by Teams Phone.

Configuration decisions

• Shared versus dedicated numbers. UK clients usually want a dedicated UK toll number with English as the default language and a toll-free number only if they're paying for callers.
• Which number is the default on invites for each organiser's region; multi-country organisations should set this per region.
• Whether toll-free is offered, and the Communications Credits funding and auto-recharge that goes with it.
• Dial-out policy: international allowed for everyone, domestic only, or blocked for most users with a carve-out group.
• PIN length and entry/exit announcements on the bridge.
• Whether dial-in callers bypass the lobby — a meeting policy setting, off by default.

Gotchas

• Toll-free without Communications Credits simply fails. Same for international dial-out. Sort the credit balance and alerts before go-live.
• Shared numbers can't have custom languages; a client wanting bridge prompts in anything other than the default language needs a dedicated number.
• New numbers can take a day to appear on invites. Existing meetings keep the old details until the organiser updates the invite.
• Dial-in callers, PSTN participants and Teams devices can't be moved into breakout rooms.
• The dial-out policy also controls the user's own PSTN calling restrictions. Pick the instance carefully or you'll block someone's Teams Phone international calling by accident.
• Webinars have no dial-in. Organisers who need phone joiners should schedule a normal meeting.

Consultant notes

• Check E5 coverage first — half the "do we need Audio Conferencing?" conversation disappears when the organisers are already on E5.
• Port existing conferencing numbers from the old provider if they're printed on materials; it saves reprinting and confusion.
• Set up Communications Credits low-balance alerts and give finance an owner; a drained balance on the day of a board meeting is a bad call.
• Document which number each region uses and test dial-in from a mobile on each before cutover.
• When migrating from a third-party bridge, reissue recurring invites after licensing — the number only lands on new or updated invites.

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Worth revisiting after the next change to Teams SKU bundling, or if Microsoft changes how Audio Conferencing is included in Teams Enterprise