To update Office 2021 on Windows, open Word or Excel, go to File > Account > Update Options > Update Now, then let Office download and install the latest build. Retail versions (Home & Business, Professional Plus with a retail key) update themselves by default; volume versions (LTSC, MAK key) may not show this button and update in a different way. Since 13 October 2026, Office 2021 keeps working, but Microsoft no longer releases fixes for it: installing the latest available build is therefore still the first thing to do.
Here is the complete method as we apply it in support: check your version, force the update, deal with cases where the button doesn't appear, and know what to do now that support has ended.
How do you update Office 2021 on a Windows PC?
Office 2021 uses Click-to-Run technology: there's no "service pack" to download, as Office fetches new builds itself from Microsoft's servers. The manual procedure takes two minutes:
- Open an Office app, for example Word, and create a blank document.
- Click File > Account (in Outlook: File > Office Account).
- In the Product Information area, click Update Options.
- Choose Update Now. If only the Enable Updates option is offered, click it first, then try again.
- Close your documents when Office asks: the installation can't replace files that are in use.
- Wait for the message "You're up to date!" or "Updates were installed".
The same menu also offers Disable Updates, View Updates (the change log) and About Updates. Our advice: never disable automatic updates on a work machine unless you have a specific constraint (an incompatible business application, for example). Microsoft describes the same procedure on its page How to update Microsoft 365 or Office for Windows.
What is the latest version of Office 2021 and how do you check yours?
To find your version, stay in File > Account and look at the line under About Word: you'll see, for example, "Version 2609 (Build 20430.20092 Click-to-Run)". Click About Word to also see the architecture (32-bit or 64-bit).
Be careful: the numbering differs depending on the licence type. It's the most frequent source of confusion in our tickets: a customer on LTSC sees "Version 2108" and thinks they're three years behind, when they're perfectly up to date.
| Criterion | Office 2021 retail | Office LTSC 2021 (volume, MAK) |
|---|---|---|
| Example editions | Home & Business, Professional, Professional Plus retail | LTSC Professional Plus, LTSC Standard |
| Version number | Changes every month (e.g. 2609 in September 2026) | Stays fixed at 2108, only the build changes |
| Latest build listed as of 22 Sept 2026 | Version 2609 (build 20430.20092) | Version 2108 (build 14334.20918, 16 Sept 2026) |
| Update channel | Managed automatically by Office | PerpetualVL2021 |
| "Update Options" button | Yes | Not always (often just "About") |
| New features | No, security and quality only | No, security and quality only |
The official build history, retail and LTSC, is published on Microsoft Learn in the Office 2021 update history. Compare the build shown in File > Account with the first line of the table that matches your licence: if it's the same, you're up to date. To better understand the difference between these two licence families, read our comparison Office LTSC 2021 vs Office 2021 Professional Plus.
Why doesn't the "Update Options" button appear?
If the Product Information area only shows the About button, three causes come up in practice:
- Volume licence (MAK/LTSC): this is normal. Office still updates in the background from the PerpetualVL2021 channel, unless the administrator has disabled it. You can force the update from the command line (see below).
- Group Policy or registry: on a company PC, the "Enable Automatic Updates" policy may be disabled, or an internal update path (file server, Configuration Manager) may be enforced. In that case, the IT department controls the builds.
-
Installed with the Office Deployment Tool using
Updates Enabled="FALSE": common on machines prepared by a service provider. You need to reinstall with a configuration that re-enables updates.
Conversely, if you see Enable Updates, someone (or a PC "optimiser") has simply turned the option off: one click is enough to restore it.
How do you force an Office 2021 update from the command line?
When the interface offers nothing, or to update several machines without opening Word, you use the Click-to-Run client directly. Type cmd in the Start menu search, right-click Command Prompt > Run as administrator, then enter:
"C:\Program Files\Common Files\microsoft shared\ClickToRun\OfficeC2RClient.exe" /update user
The Office update window opens and downloads the latest build for your channel. Two useful options:
-
forceappshutdown=truecloses Word, Excel or Outlook if they're blocking the installation (save your files first). -
updatetoversion=16.0.xxxxx.xxxxxinstalls a specific build. We mainly use it to roll back temporarily to the previous build when an update breaks a business add-in.
To check the installed version without opening Office, query the registry:
reg query "HKLM\SOFTWARE\Microsoft\Office\ClickToRun\Configuration" /v VersionToReport
Automatic updates rely on the Office Automatic Updates 2.0 scheduled task (Task Scheduler > Library > Microsoft > Office) and on the Microsoft Office Click-to-Run Service (ClickToRunSvc). If either is disabled, Office no longer updates itself. It's the first thing we check after a "clean-up" tool has been run.
The update fails: what should you check?
Most of the Office 2021 update failures we handle are fixed with the same sequence:
- Connection: a corporate proxy, VPN or filtering DNS can block Office's content delivery servers. Test on another connection (a mobile hotspot, for example).
- Disk space: allow at least 4 to 5 GB free on C:, as the new build is downloaded before replacing the old one.
-
Click-to-Run service: type
services.mscand check that Microsoft Office Click-to-Run Service is set to Automatic start-up and running. - Quick Repair: Settings > Apps > Installed apps > Microsoft Office Professional Plus 2021 > Modify > Quick Repair. It doesn't need the internet.
- Online Repair: if the failure persists, same path with Online Repair. Office is reinstalled at its latest build; your licence and files are kept.
If Office asks for a key again after an online repair, keep your product key to hand. Customers who have changed PC in the meantime will find the steps in our guide to reinstalling Office 2021 on a new PC.
Can you upgrade Office 2021 to Office 2024?
No, and it's a question we're asked every week. Office 2021 updates stay within version 2021: security and stability fixes, no new features, no major version change. No option in File > Account turns Office 2021 into Office 2024.
Moving to Office 2024 requires a new licence, uninstalling Office 2021 and then installing Office 2024. Your documents aren't affected: the .docx, .xlsx and .pptx formats are identical. If you're torn between keeping your current version and switching, our comparison Office 2024 vs Office 2021: which to buy covers what's genuinely new in 2024.
What happens to updates after 13 October 2026?
Support for Office 2021, both retail and LTSC, ended on 13 October 2026, with no paid extension. In practice, according to Microsoft's page End of support for Office 2021:
- your Office 2021 apps keep working, and your licence remains valid and activated;
- Microsoft no longer releases security fixes or bug fixes for Office 2021;
- technical support by phone or chat is no longer provided for this version.
What we recommend to customers who are keeping Office 2021:
- run Update Now one last time to get the builds released up to the end of support;
- leave automatic updates on: they do no harm and will pick up anything still being distributed;
- keep Windows and Microsoft Defender up to date, and leave macros in downloaded files blocked (the default behaviour);
- be careful with Office attachments received from outside: they are the main attack vector on an unmaintained suite.
For personal use or a small office, Office 2021 remains usable under these conditions. For an exposed machine (accounting, exchanging files with outside parties), Office 2024, supported until October 2029, is the forward-looking option. The scenarios are covered in detail in our article on Office 2021 end of support and what to do.
What about Office 2021 for Mac?
On a Mac, updates don't go through File > Account but through Microsoft AutoUpdate. Open Word, then the Help > Check for Updates menu, tick Automatically keep Microsoft Apps up to date and click Update. Office Home & Business 2021 for Mac follows the same timeline: support ended on 13 October 2026. Also keep macOS up to date, as each build of Office for Mac requires a minimum system version.
Frequently asked questions
Does updating Office 2021 delete my documents or my licence?
No. An update only replaces the program files. Your documents, templates, Outlook profile and activation stay in place.
How long does an Office 2021 update take?
A monthly update usually downloads a few hundred MB and installs in 5 to 15 minutes depending on the connection. An online repair, which reinstalls everything, takes longer.
My version shows 2108: am I behind?
Not necessarily. Volume licences (LTSC, MAK) stay on version 2108 and only the build number changes. Compare your build with the official update history.
Should you turn off updates now that support has ended?
No. Leaving updates on has no downside and ensures you have the latest published build.
Does Windows Update update Office 2021?
Not the Click-to-Run version sold today: it updates via its own service and the Office Automatic Updates 2.0 scheduled task. The Windows Update option "Receive updates for other Microsoft products" mainly concerns older MSI installations.
Move to a supported version when you're ready
If your Office 2021 is up to date and meets your needs, there's no rush: it keeps working. When you want a suite that still receives security fixes, Office 2024 Professional Plus for Windows installs with a perpetual licence key, with no subscription. You can also browse our full Office 2021 range if you're equipping an extra machine with the same version as the rest of your fleet. If you're unsure about your version or update channel, our support team will help if you send a screenshot of File > Account.