ACS retirement: what lands on Teams voice

What it does

Microsoft is retiring Azure Communication Services as a standalone offering on 30 September 2028. The voice parts that survive only stay supported when they run as a Teams scenario: Teams Phone extensibility, Teams meeting interop or Click-to-Call for Teams voice apps. In practice, programmable voice that used to live in its own Azure silo now hangs off Teams Phone. This doc covers what that means for a Teams voice estate. The Contact Center side is in the D365 Contact Center KB.

Key facts

Announced in September 2026. Retired services stop on 30 September 2028.
From 23 October 2026, new customers can't sign up for the retiring services. Tenants with an ACS resource created before then keep access through the transition. The Dynamics 365 guide uses 30 September 2026 for the number-acquisition cut-off, so check which date applies to the tenant in front of you.
Retired outright: ACS Direct Routing, Number Management (Direct Offer numbers), Email, SMS, WhatsApp, Chat (including Teams meeting interop chat), Rooms, Job Router, and the Web and Mobile UI Libraries.
Breaking change, stays only for Teams-aligned use: Calling SDK, Call Automation, Call Diagnostics, Audio Streaming, Call Recording and Closed Captions. These move to a new major SDK version.
Not affected: Teams Phone, Teams interop and Teams Phone extensibility (TPE).
ACS Direct Routing moves to Teams Direct Routing or Operator Connect. ACS numbers move to a Calling Plan, Operator Connect, Teams Direct Routing or TPE.
The same SBC FQDN can't be registered against ACS Direct Routing and Teams Direct Routing at the same time.
Call Automation after 2028 is supported only for documented Teams scenarios, mainly TPE. Bolting an AI service onto a standalone PSTN flow doesn't make it a Teams scenario.
Not every Call Automation feature works under TPE, so check the TPE capability matrix before promising a migrated IVR.
Retiring services get break-fix and security fixes only until 2028. Breaking-change services keep GA support but no committed new features.

When to use / skip

You only need this if something in the estate touches ACS. That might be a custom IVR or outbound dialler built on Call Automation, an ACS Direct Routing trunk, ACS-bought numbers, or a contact centre vendor on the Unify model. A pure Teams Phone estate on Calling Plans, Direct Routing or Operator Connect isn't affected. Ask anyway: ACS tends to turn up in a side project the voice team never heard about.

For anything new, design on Teams Phone and TPE from day one. Treat an ACS-only voice design as legacy.

Configuration decisions

Where each ACS number goes: Calling Plan, Operator Connect, Teams Direct Routing or onto a TPE resource account. Decide per range, not per tenant.
Cutover or coexistence for the SBC. A full cutover means removing the FQDN from ACS and living with a propagation gap. Coexistence means a second FQDN and a certificate that covers both.
Licensing. Every number that moves needs a Teams resource account with a Teams Phone licence, plus a Calling Plan where Microsoft is the carrier. ACS shops usually haven't budgeted for that.
Rebuild custom Call Automation flows on TPE or hand them to a certified vendor. Check the capability matrix first.
Recording. Built-in ACS recording files are downloadable for only 24 hours. Either move to Bring Your Own Storage now or plan how recordings get archived.

Gotchas

The near-term deadline is the new-customer cut-off in autumn 2026, not 2028. A project that assumed it could spin up a fresh ACS resource and buy numbers needs a new plan.
TPE doesn't honour Teams compliance recording. If the regulatory recording obligation is met by a policy-based recorder, calls moved onto TPE fall outside it.
A Global voice routing policy left with Direct Routing patterns will grab calls meant for Operator Connect. Use named policies once the ACS trunk comes across.
Releasing ACS numbers before they've ported is the one mistake you can't take back. Remove numbers before deleting the resource too, or orphaned numbers keep billing, and getting them released means a support ticket.
ACS and Teams use different media address ranges. Firewall rules for a migrated SBC are rebuilt, not copied.
The Calling SDK for meeting interop doesn't bring the server-side features with it. Recording, WebSocket streaming and transcription inside a Teams meeting still need a supported Call Automation scenario.

Consultant notes

Run an ACS discovery in every Teams voice engagement from now until 2028. Check the Azure subscriptions for Communication Services resources and ask the contact centre vendor which certification model they're on. Unify vendors are on ACS by definition.
Frame it to the client as a licensing conversation first. The technical moves are well trodden. The new Teams Phone and resource account lines are what the sponsor hasn't seen.
For the SBC move, get the network team in early. The FQDN, the certificate SANs and the firewall ranges all sit with them.
Keep the old ACS trunk and numbers alive until inbound, transfers, voicemail and emergency calling have run cleanly for a full business cycle on the new path.

Revisit when the October 2026 cut-off has passed and again when Microsoft publishes TPE capability updates — the Call Automation gaps are the ones to watch