Office 2021 End of Support: What UK SMEs Should Do Now

Microsoft stopped issuing security fixes for Office 2021 and Office LTSC 2021 on 13 October 2026. Word still opens. Excel still recalculates. That is why so many businesses have not noticed.

The applications were not switched off. They are unsupported, which means no patches for newly discovered vulnerabilities, no bug fixes and no technical support from Microsoft. A device running them works until it does not, and the failure is usually a document that will not open, a macro that throws an error, or an exploit that nobody can fix.

For the past fortnight we have been answering the same question from clients: do we have to move now? For most UK SMEs the answer is yes, and the cheapest supported route is rarely the one people expect.

What ended on 13 October

Microsoft's lifecycle notice is short and blunt. Office LTSC 2021 reached end of support on 13 October 2026, and from that date Microsoft provides no technical support, bug fixes or security updates. The same date closed support for Project LTSC 2021, Visio LTSC 2021 and the retail Office 2021 suite.

Office 2019 and Office 2016 ended on 14 October 2025, so a business that skipped that upgrade is now two generations behind. We still find Office 2016 on finance laptops more often than anyone would like to admit.

Publisher has its own deadline. It was removed from Microsoft 365 subscriptions on 1 October 2026, and the perpetual version lost support on the same 13 October date. A subscriber cannot open a .pub file in Publisher any more. Anyone holding a licensed perpetual copy can reinstall it and keep working, but there are no fixes and Microsoft has published no replacement product, only guidance on moving those layouts to Word and PowerPoint.

The compliance problem lands before the security one

Most of the incidents we are called into do not begin with an Office zero-day. The practical damage arrives earlier, in the paperwork that wins and keeps work.

Cyber Essentials is the clearest example. The current requirements are version 3.3, published in April 2026, and they state that all software on in-scope devices must be licensed and supported and must be removed when it becomes unsupported. The certification question set is explicit: unsupported software comes off the device, or the device moves to a defined sub-set with no internet access. There is no grace period for an application that stopped receiving fixes a fortnight ago.

Two further requirements make the position hard to argue around. Critical and high-risk vulnerability fixes have to be installed within 14 days of release, and in-scope devices need automatic updates enabled where the software allows it. A product with no vendor fixes cannot satisfy either test. If your business needs Cyber Essentials for a public sector bid, a framework agreement or an insurance renewal, Office 2021 is now a failed answer on the form rather than a judgement call.

Client and insurer questionnaires ask the same question in softer language. Which applications are out of support, and when will they be replaced? An honest answer of "Office 2021, no date" has cost businesses work we know of. It is a slower and less dramatic loss than ransomware, and far more common.

Four routes, and what each costs

Microsoft's upgrade guidance for older Office versions points organisations with fewer than 300 users at Business Premium, Business Standard or Microsoft 365 Apps for business, with Office LTSC 2024 kept for machines that cannot take continuous updates. Those are the options worth costing. The prices below are Microsoft's published UK figures, excluding VAT, on an annual commitment.

Two lines in that table deserve a second look. Microsoft 365 Apps for business at £9.80 supplies the desktop applications and 1 TB of storage but no hosted business email, so it only works if your mail already lives somewhere you are keeping. Business Standard at £10.80 adds a mailbox, Teams and the ability to answer a client from a phone.

Paying £9.80 for apps-only when £10.80 buys apps plus business email and Teams is one of the worst value decisions in Microsoft licensing. We see it regularly, usually because a feature list was compared quickly and nobody noticed email was never included. A pound a month per user is £12 a year. It decides whether a member of staff can read a proposal on a train.

The Copilot bundles have a similar trap. Business Standard with Copilot costs £18.10, which is £1.20 more than Business Premium without it. A firm with client data and no device management should fix the security gap before buying AI seats on the cheaper tier. Our Copilot readiness work starts with that decision, because Copilot on an unmanaged device with open sharing is an expensive way to expose files.

Where Office LTSC 2024 is the right answer

Office LTSC 2024 is supported until October 2029 and bought as a one-time purchase per device through volume licensing. It carries no feature updates after release, no Copilot and no Publisher, and Microsoft positions it for regulated devices that cannot accept change, process control machines on a factory floor and systems that never connect to the internet.

For a machine controlling a production line, that is a sensible fit. Forty desks in an office are a different proposition: LTSC delays a decision you will make anyway, and you pay for it twice, once now and again before 2029. Ask for a written three-year cost per device. If it lands anywhere near Business Standard, the subscription wins on email, Teams, storage and management alone.

Three-year cost for a 25-person business

Those figures exclude partner margin and any reseller discount, and they assume no further price changes. Microsoft has moved UK business pricing twice in two years, so treat the third column as a planning number rather than a forecast. The gap between Standard and Premium for 25 people is £5,490 over three years, which works out at £73.20 per user per year for Defender for Business, Intune, Entra ID P1 and conditional access.

Mailbox storage has moved in the opposite direction. Business suites now carry a 100 GB maximum primary mailbox, up from 50 GB, after a service plan change that rolled out between June and September 2026. That matters if you are moving staff off an ageing Exchange plan. The quota is a supported maximum rather than a promise, both service plans have to be enabled on the user, and it does not include an archive. If you are moving mail as well as Office, our Exchange to Microsoft 365 migration work runs alongside the desktop deployment rather than after it.

What breaks, and the order to fix it

Deployment is the easy part. The friction sits in details nobody documented.

• Remove the old build first. Installing Microsoft 365 Apps over a device that still has Office 2021 registered causes activation errors and file association problems that can eat a day.
• Retire the volume licensing. MAK keys and KMS servers from the 2021 estate have to go, or rebuilt laptops quietly reactivate the unsupported version.
• Test the add-ins. Finance add-ins, document management tools and old Excel macros are where upgrades stall. Five pilot users on real workbooks find more than any checklist.
• Check legacy files. .xls and .doc files with macros may open in Protected View, and changing that is a policy decision rather than a click.
• Turn on Known Folder Move. Staff files sitting on laptops are the exposure everyone forgets, and OneDrive gives you the copy people assume already exists.
• Rebuild templates and signatures. Brand templates built for 2021 sometimes reflow, and signatures tied to an old Outlook profile need redoing.
• Record the evidence. A dated software inventory, a licence count and a screenshot of the deployed version are what an assessor asks to see.

What this looks like on a real site

Last month we worked with a 45-person professional services firm running a mixture it had never documented: Office 2019 volume licences on most desks, retail Office 2021 Home and Business on three director laptops bought from a high street retailer, and a handful of staff on Exchange Online Plan 1 with 50 GB mailboxes.

Nobody held a licence inventory, so the first job was counting what was installed rather than what had been bought. Two of the retail copies were tied to personal Microsoft accounts belonging to former employees, which is a licensing problem and an access problem at the same time. The upgrade itself took four days. Finding and fixing the spreadsheet add-ins the finance team relied on took six more, and the Publisher files behind their printed service brochures were converted to PDF by the one person who knew where they were saved.

The migration was not the difficult part. Building the inventory was, and the licensing decision took an afternoon once we knew what the business actually held.

A 30-day plan

Thirty days is enough for most businesses under 100 users, provided the licence decision happens in week one rather than week four.

• Week one: inventory every device, the Office version on it and how that copy is licensed. Include the laptops that never touch the network.
• Week one: decide per role rather than per person. Frontline, office-based, and anyone handling client data or a shared device.
• Week two: pilot with five users on the messiest workbooks and the oldest templates.
• Week three: deploy in batches, removing the old build on the same visit, and confirm activation in the admin centre.
• Week four: retire the old keys, convert any remaining .pub files, and file the evidence with your Cyber Essentials records.

Two things go wrong in that plan more than any other. Licences get bought before anyone knows which staff need desktop Excel, and the volume licence keys stay active so half the estate quietly reverts after a rebuild.

Microsoft's end of support notice for Office LTSC 2021 sets out the upgrade paths Microsoft will stand behind, and it is worth reading before you brief a supplier. The Cyber Essentials requirements for IT infrastructure give you the wording an assessor will use when they ask about unsupported software. Both documents are short, and both are useful in a budget conversation.