In many of the environments I work with, Office LTSC 2021 end of support is climbing the priority list fast. The date to remember is 13 October 2026. From then on, neither Office LTSC 2021 nor the Office 2021 retail version gets updates. There is no extended support phase and there are no late security patches. Just as important, connecting to Microsoft 365 services is no longer officially supported. That is a real risk with a deadline attached. Old Office installs tend to survive on forgotten lab machines, at remote sites or inside legacy VDI images, and if nobody goes looking for them, you end up with broken workflows and vulnerabilities in your tenant. Microsoft's Office LTSC 2021 lifecycle page leaves no doubt that it's time to act.

Every Office LTSC 2021 project starts with discovery

On paper, everyone knows where Office is installed. In practice, installs turn up in odd places. Even in tenants that moved to Microsoft 365 Apps years ago, I still find Office LTSC 2021 on break-glass devices, on factory floor PCs and on jump hosts nobody logs into anymore. Fortunately there are a few dependable ways to see what's actually out there:

  • Intune → Apps → Discovered apps: Shows which version (Office LTSC 2021 included) sits on each Intune-managed device. The data is current, but it only covers enrolled endpoints.
  • Microsoft Defender Vulnerability Management (Defender for Endpoint Plan 2+): Under Software Inventory, filter for "Microsoft Office LTSC 2021" or "Office 2021" and you get a reliable picture across managed PCs and servers.
  • Configuration Manager: Its inventory view still gives you a complete list of Office installs, which helps most in hybrid environments with older endpoints.

I often turn up extra copies by searching for leftover setup files, or they surface during OS upgrade projects. Using more than one tool catches more of the odd cases, and exporting the results to CSV makes it easier to get stakeholders on board and track progress.

You either replace the perpetual version or move to the subscription

The choices are simple, even if the work isn't. Microsoft offers no extension and no paid patching, so replacement has to be planned. In real projects I see two main paths:

  1. Move to Office LTSC 2024. If you need a perpetual license (no subscription), Office LTSC 2024 is the only supported option. It has the same five-year support window (Office LTSC 2024 overview) and a classic feature set, which means no Copilot, no AI and no cloud-first features. I wrote about where it fits and where it doesn't in Office LTSC 2024: Where the perpetual licence fits (and fails).
  2. Migrate to Microsoft 365 Apps. If your users need ongoing updates and cloud features, or want to use the Microsoft 365 ecosystem properly, the subscription model is the obvious choice. You get regular feature and security updates, Copilot, and proper support for all Microsoft 365 services.

Either way, plan carefully. Licensing, add-in compatibility, macro support and the rollout mechanics all play a part. Running several Office versions on one device, or even across one environment, reliably produces support trouble. Start testing early, particularly when going from LTSC 2021 to Microsoft 365 Apps, and standardize your update channels to keep things manageable.

Support for connecting to Microsoft 365 services ends as well

This is the part that catches admins off guard. When support for Office LTSC 2021 ends, official connectivity to Microsoft 365 services ends with it, and that includes Exchange Online, SharePoint Online and Teams. Some things will keep working for a while, but new features may stop showing up, and core functions such as modern authentication or add-ins can break without notice. I'm already seeing more tickets of this kind (missing Teams add-ins, Outlook dropping its connection, users who suddenly can't join meetings) because older Office builds are falling out of compatibility.

Keep an eye on Microsoft 365 Admin Center → Health → Message Center for announcements about upcoming restrictions. Still, the only safe option is to get rid of Office LTSC 2021 before 13 October 2026. Otherwise you're simply waiting for the next support incident.

The Office Deployment Tool removes Office LTSC 2021 at scale

Whichever path you choose, you'll probably need to automate the removal. The Office Deployment Tool (ODT) is the tool I rely on for this. It's dependable, it can be scripted, and it works with Intune Win32 apps or SCCM packages for large rollouts.

A sample removal XML for ODT looks like this:

<Configuration>
  <Remove>
    <Product ID="ProPlus2021Volume" />
  </Remove>
  <Display Level="None" />
  <Property Name="FORCEAPPSHUTDOWN" Value="TRUE" />
</Configuration>

This requires local admin rights. Change the Product ID to match the editions you actually have (for example Standard2021Volume for Standard). Test the removal on representative devices before you push it broadly.

Pro tip: Always include the "FORCEAPPSHUTDOWN" property in your removal config. It prevents hung processes and user prompts, which matters most for remote or unattended deployments.

The migration follows a predictable workflow

To make the usual migration a bit more concrete, this mermaid diagram shows the practical flow from discovery through to checking the result:

flowchart TD
  Scan["Discover installations"] --> Decide["Plan migration or removal"]
  Decide --> LTSC2024["Deploy Office LTSC 2024"]
  Decide --> M365["Deploy Microsoft 365 Apps"]
  Decide --> Remove["Remove Office LTSC 2021"]
  Remove --> Verify["Verify success"]
  LTSC2024 --> Verify
  M365 --> Verify

Figure: Typical project workflow for replacing Office LTSC 2021 installs.

Verification comes last, and you shouldn't skip it. Unless you check for leftover Office components and test the important workloads after the migration, edge cases slip through easily.

I recommend starting early and documenting everything

Office LTSC 2021 end of support doesn't come as a surprise, yet in most organizations the actual work is only now getting started. A complete inventory, structured pilots and a clear decision between LTSC 2024 and Microsoft 365 Apps will save you trouble later. Leave yourself some slack and don't push this into the final quarter. Planned migrations go more smoothly and cost less, and you keep unnecessary risk away from your Microsoft 365 environment.