Office 2016 and 2019 Are Out of Support, Office 2021 Ends on 13 October 2026: Moving to Microsoft 365 Apps Without Breaking Anything

Three dates matter here, and only one of them is still ahead of you.

Office 2016 and Office 2019 reached end of support on 14 October 2025. No security updates, no bug fixes, no technical support, and Microsoft offered no Extended Security Updates program to buy more time.

Office LTSC 2021 and the retail Office 2021 editions reach end of support on 13 October 2026. Visio LTSC 2021 and Project LTSC 2021 go on the same day. Again, there is no extended support phase and no paid ESU program: Windows 10 got a paid bridge, Office did not.

Office LTSC 2024 is Microsoft's current on-premises release. It sits under the Fixed Lifecycle Policy with five years of support and no extended phase, ending 9 October 2029.

If you track these alongside the rest of the Microsoft calendar, we keep a running list of Microsoft deadlines with what each one changes.

Nothing switches off on the deadline. Word opens on 14 October 2026 the same way it opened the day before, and that is the whole problem: the risk arrives quietly and never announces itself.

What changes is that every vulnerability found after the date stays unpatched forever. Office clients are a well-worn way into a network, because the attack arrives as an ordinary business file: an invoice, a resume, a spreadsheet from a supplier. An unpatched parser or macro engine on hundreds of desktops is a standing invitation, and it does not matter how good your email filtering is if the client behind it can no longer be fixed.

The second cost shows up on paper. Cyber insurance questionnaires ask whether you run unsupported software. So do SOC 2 auditors, CMMC assessors, and the security review your largest customer sends every year. "Office 2019, unsupported since October 2025" is an answer that costs you either a premium, a finding, or a contract.

Microsoft supports connections to Microsoft 365 services, including Exchange Online, SharePoint Online and OneDrive, only from Office versions that are still in support. Support for Office 2016 and Office 2019 connecting to those services ended on 10 October 2023, well before the apps themselves went out of support.

Microsoft does not flip a switch on the date. Older clients may keep connecting. But they are no longer tested against service changes, features added to the service after the cut-off may simply not work for them, and any performance or reliability problems that follow will not be fixed. You are running an untested client against a service that changes every month.

On 13 October 2026, Office 2021 joins that category. If your mailboxes are in Exchange Online and your documents are in SharePoint or OneDrive, this is the part that bites first, and it usually shows up as an Outlook profile that stops behaving for one user, then another, with no obvious cause and no fix available.

Microsoft 365 Apps is the subscription version of the desktop apps. It updates itself on a channel you choose, and as long as you keep it on a supported build, it stays supported for connecting to Microsoft 365 services, which is the one thing a perpetual licence can never promise for long. For most organizations already paying for Microsoft 365, it is also the version they are entitled to and are not using.

Office LTSC 2024 is the perpetual path: buy once, licensed per device, no feature updates, supported to 9 October 2029. It is the right answer for machines that are deliberately frozen, such as a manufacturing terminal, a lab PC, or a device with no reliable internet connection. It is the wrong answer for a normal office desktop, because you will be having this same conversation again in three years.

A mix is legitimate. Subscription apps for the people who live in email and shared documents, LTSC for a short list of locked-down machines with a named owner and a written reason.

Doing nothing is also a decision, and it is the only one with no end date. It carries an unpatched client, an unsupported connection to your own tenant, and an audit answer you have to keep writing.

Before you buy anything, check what you already own. Microsoft 365 Apps is included in most Microsoft 365 business and enterprise plans, and a surprising number of desktops run a perpetual Office licence next to a subscription that already includes the same apps. A Microsoft 365 license audit answers that in a week, and if you are weighing perpetual against subscription across several agreements, our Microsoft volume licensing assessment is the place to start.

The migration itself is not hard. It goes wrong when it is done in the wrong order, or all at once.

First, inventory. Which Office versions and builds are actually installed, 32-bit or 64-bit, installed by MSI or by Click-to-Run, and on which machines. The answer is almost never the one in the asset spreadsheet.

Second, settle licensing before you touch a desktop, so nobody installs an app the tenant will not activate.

Third, pick the deployment vehicle. On managed Windows devices that is Intune, which pushes Microsoft 365 Apps with the architecture, language and channel you specify, and removes the old build as part of the same install rather than leaving two versions fighting over file associations. If Intune is not set up yet, that is its own short project: Intune initial setup for Windows builds the enrollment foundation, the security baseline and the first application assignments, including Microsoft 365 Apps where licensed.

Fourth, choose one update channel and write it down. Monthly Enterprise Channel is the usual middle ground for business fleets: predictable, once a month, testable. Windows Autopatch can take Microsoft 365 Apps updates off your desk entirely once the fleet is on a channel.

Fifth, pilot with 10 to 20 people chosen for their awkwardness, not their patience: the finance analyst with the macro workbook, the person who still uses mail merge, the team with the ancient add-in. Then run the rest in waves of a department at a time, with the helpdesk warned in advance.

Sixth, decide who keeps it healthy afterwards. Channels drift, add-ins update, new devices arrive. Managed Intune exists because most estates are clean on handover day and unrecognizable a year later.

This is the list that turns a two-week rollout into a two-month one when it gets skipped.

• Macros and VBA. They mostly carry over, but 32-bit to 64-bit moves and old ActiveX controls do not.
• COM add-ins, especially from CRM, accounting, practice management and document management vendors. Check the vendor's supported versions before, not after.
• Access databases. Confirm the app is included in the plan you are moving to, and identify who owns each database.
• Publisher files. Publisher is being retired: it is removed from Microsoft 365 subscriptions after 1 October 2026, and support for the perpetual version ends 13 October 2026 with the rest of the 2021 family. Export what matters to PDF, and move the live documents into Word or PowerPoint while someone still remembers how they were built.
• Shared templates, custom dictionaries, signatures and Normal.dotm sitting on a file share.
• Multifunction printers and scanners that send mail through a desktop Outlook profile.
• Line-of-business apps that export to Excel or generate Word documents through automation.
• Anything with a hard-coded path to an old Office install location.

Every one of these has an owner somewhere in the business. Find them during the inventory, not during the cutover weekend.

Windows 10 went out of support on 14 October 2025. If part of your fleet is still on it, sequence the two moves together rather than touching each desktop twice; Windows 11 migration and Windows 10 ESU transition covers the hardware assessment, the in-place upgrades and the ESU bridge for machines that cannot take Windows 11 yet. Microsoft's ESU fees are Microsoft's charge and land on your bill, which is the argument for making the bridge short.

The Office move is not blocked by a Windows 10 fleet. Microsoft has committed to security updates for Microsoft 365 Apps on Windows 10 until 10 October 2028, so the apps can go first. That is a grace period for the apps, not for the operating system underneath them.

And if you have no tenant at all, which is common for organizations still running perpetual Office next to POP mail or an old on-premises server, the Office question is really a tenant question. Microsoft 365 new tenant setup is the front door: domain, identity, mail, and a security baseline, before anything gets installed on a desktop.