Your Copy of Office 2021 Stops Getting Security Fixes on October 13

Five years. That is roughly how long Microsoft supports Office 2021, and it is about half the decade that Office 2016 got. Plenty of owners bought Office 2021 in 2022 or 2023 as a one-time purchase precisely so they would never have to think about a subscription again. End of support for that purchase arrives on October 13, 2026, which is three weeks away.

Nothing dramatic happens on the day, and that is the trap. The apps open and the files save, while every newly discovered hole in Word, Excel and Outlook stays open on that machine for good. Below: who is affected, what the fix costs, and how to finish before the date.

Quick answers

Will Office 2021 stop working on October 13? No. Word, Excel and Outlook keep starting and your files stay readable. What ends is the flow of security fixes, bug fixes and technical support. Microsoft says plainly that continuing on an unsupported version raises your exposure to security risks and can affect compliance requirements.

Does it also cover Office bought as a one-time purchase, not through Microsoft 365? Yes. Microsoft's support page for Office 2021 lists Home & Business 2021 with the same October 13, 2026 date as the volume-licensed LTSC edition.

Can we simply buy Office 2024 instead? You can, and Microsoft names Office LTSC 2024 as the on-premises path. It is sold for one device per license and aimed at regulated, offline or fixed-function machines. For ordinary office PCs a Microsoft 365 plan is the better fit.

What does the switch cost? From July 1, 2026 Microsoft lists Business Standard at $14 per user per month and Business Premium at $22. For 15 people that is $2,520 or $3,960 a year, and both include the desktop apps.

Which of your Office installs does this actually hit?

Most small offices are not running one version. A typical company has a mix: the PCs bought new in 2022 with Office 2021, a few older machines still on 2019, and the newest laptops on a Microsoft 365 subscription. Open any Office app, click File, then Account, and the product name is printed at the top. Do that on one PC per department and you will have your answer for most of the office.

The end-of-support dates for the older versions come from Microsoft's upgrade guide for older Office versions. If you find 2019 or 2016 anywhere, treat it as more urgent than the 2021 copies, because it has already lost its patches.

What does Office 2021 end of support change on October 14?

Three things, and only the first is obvious. Security fixes stop, so a flaw found next month in Outlook's handling of attachments will be fixed for Microsoft 365 users and left open for you. Technical support stops, which means Microsoft will not troubleshoot a problem on that install. And the connection to your cloud services becomes unsupported.

That last one deserves a closer look. Microsoft publishes a list of Office versions that are supported for connecting to Exchange Online, SharePoint and OneDrive. Office LTSC 2021 is on it only until October 13, 2026. Older versions can still connect, Microsoft notes, but they may miss newer features and can develop reliability problems, because improvements to the cloud services are not tested against them. Outlook is where an owner would first feel that, as a mailbox that syncs strangely or a calendar that behaves differently on one PC than on the next.

Then there is your insurer. Cyber insurers have started to treat out-of-support software as its own risk class, and an overview of 2026 policy wording describes claims being contested where the software inventory a company declared did not match what was running. If your renewal questionnaire asks about unsupported software, the honest answer changes on October 14. Your IT governance and compliance paperwork should reflect that.

Is Office 2024 the simple answer, or is it another dead end?

Microsoft's own recommendation splits by situation. Organizations not ready for the cloud are pointed to Office LTSC 2024, and everyone else to Microsoft 365 Apps. Both are legitimate. They solve different problems, and the difference shows most clearly side by side.

The Copilot row comes from Microsoft's own September 2026 partner announcement, which states that Microsoft 365 Copilot is supported only on the cloud-backed apps in Microsoft 365 suites, not on on-premises Office. You may not want Copilot today. Buying a version that can never run it is a decision worth making with your eyes open.

What does switching cost a 15-person office?

Take the list prices Microsoft set from July 1, 2026. Business Standard is $14 per user per month, which for 15 people is $2,520 a year. Business Premium is $22, or $3,960 a year. The standalone Microsoft 365 Apps plan lists at $14 as well, per the same Microsoft pricing notice, so it rarely makes sense unless your email lives somewhere else. Standard adds business email, Teams and file storage on top of the same apps.

Compare that with what you already paid. A one-time Office purchase looked cheaper because the cost sat in a single invoice years ago. The real comparison today is between $2,520 a year and a support-free product that you will have to replace anyway. If you already pay for Business Standard or Premium but still installed Office 2021 on some PCs out of habit, the fix costs nothing extra: the apps are part of your plan and only need to be installed.

The choice between the two business plans mostly comes down to security. Our breakdown of Business Standard versus Premium shows what the extra $8 buys. If you are unsure which tier fits, a Microsoft 365 licensing and support conversation before you buy saves the cost of switching plans later.

What usually goes wrong during the switch?

The installation is rarely the hard part. The surprises live in files nobody remembers. Picture a ten-person accounting practice where one Excel workbook, built years ago by someone who has since left, calculates every client's quarterly figures using macros. It works today on Office 2021. Nobody knows whether it works on the current apps, and the week before a deadline is a poor time to learn.

Microsoft's upgrade guide tells administrators to test business-critical macros, third-party add-ins and complex spreadsheets before rolling out. Do that on two PCs first. Ask each department for the three files they cannot work without and open them in the new apps. Two other details from the same guide are worth knowing. Old Office versions need to be removed before the new apps go on, because leftovers cause conflicts. And after the upgrade each user may see a "Your Privacy Matters" prompt that has to be accepted, so warn your staff, or they will call you about it on Monday morning.

Macs follow the same dates. If a designer or a partner works on a Mac with Office 2021, count that machine too.

A plan that fits into the three weeks left

October 13 is also the day the first year of Windows 10 Extended Security Updates runs out, which we cover in our piece on what Windows 10's end of support costs a business. Check both in one pass, because the PCs that still run one old product often run the other.

Here is a sequence that works for a company of 10 to 50 people:

Week one: count every install and write down the product name and edition for each PC, Mac included. Ask each department for their three critical files.

Week two: decide the license, buy it, and pilot the new apps on two PCs. Open the critical files and note anything that breaks.

Week three: roll out to everyone else in groups of five or so, remove the old version as you go, and ask the two pilot users to help colleagues with first-day questions.

Skipping ahead of week one is the usual mistake. A count that is wrong by three PCs means three PCs quietly running unpatched software next year. A structured Microsoft 365 security assessment includes exactly that inventory, and on the security side cloud security hardening only pays off when the devices behind it still get patches.