Office 2021 vs Microsoft 365: One-off Purchase or Subscription? (UK Guide)

By AutoSoftKey Editorial·Published 2 September 2026·Updated 2 September 2026·7 min read

Short answer: Office 2021 is a one-off purchase: pay once, install the classic desktop apps on a PC or Mac and use them for as long as you like, with Microsoft security updates until 13 October 2026. Microsoft 365 is a subscription (£84.99 a year for Personal, £104.99 for Family in the UK) that keeps the apps updated, adds 1 TB of OneDrive storage per person and Copilot, and stops working when you stop paying. If you want Word, Excel, PowerPoint and Outlook on one machine without a recurring bill, buy Office 2021; if you want cloud storage, several devices or the newest features, subscribe. AutoSoftKey sells Office 2021 Professional Plus from £79.95 as a pre-owned licence.

“Is Microsoft Office a one-time purchase?” is one of the most common Office questions searched in the UK, and the answer has become less obvious every year as Microsoft steers buyers towards Microsoft 365. Both options still exist. This guide compares them on the things that matter — total cost over several years, which applications you get, cloud storage, device limits, Copilot, support dates and what happens when the licence ends — and then recommends an option for each type of buyer.

Microsoft’s UK prices in this guide were read from the Microsoft Store UK and microsoft.com/en-gb on 2 September 2026; AutoSoftKey prices are the ones shown on the linked product pages at the same date. Microsoft changes prices without notice, so check the live figure before you commit.

The core difference: perpetual licence vs subscription

Office 2021 is a perpetual licence. You buy a fixed version of Word, Excel, PowerPoint, Outlook and OneNote (plus Publisher and Access in the Professional Plus edition, and Teams in the business editions), install it on one computer and keep using it indefinitely. It receives security fixes until Microsoft’s support date and then simply carries on without them. It never gains new features.

Microsoft 365 is a subscription. The same applications are delivered as continuously updated versions, tied to your Microsoft account rather than a machine, with cloud storage, mobile apps and extras bundled in. New features (and, since 2025, Copilot AI) arrive monthly. When the subscription lapses, the apps drop into a read-only mode and the storage allowance shrinks to the free 5 GB.

What it costs in the UK over one, three and five years

Subscriptions look cheap per month and expensive over time; perpetual licences are the reverse. The table uses Microsoft’s UK prices and AutoSoftKey’s pre-owned Office 2021 price for a single user.

Two caveats. Family is the best value in Microsoft’s range if six people will actually use it: £17.50 per person per year. And Office 2021’s security updates end on 13 October 2026, so a five-year horizon on Office 2021 means running it for several years without patches; Office 2024 (supported to 9 October 2029) or a Microsoft 365 plan is the safer long-term choice for a machine that handles email attachments from strangers.

Where Microsoft 365 is clearly better

• Several devices or several people. One Family subscription covers six people on five devices each. Matching that with perpetual licences means buying six of them.
• Cloud storage and syncing. 1 TB of OneDrive per person, with files and settings following you between desktop, laptop, phone and browser.
• Copilot and new features. Copilot in Word, Excel, PowerPoint and Outlook, plus every feature Microsoft has shipped since 2021 — dynamic arrays and newer Excel functions, modern comments, Designer, the new Outlook.
• Ongoing security. No support cliff to plan around.
• Business use with email hosting. Microsoft 365 Business Standard (£18.10 per user per month excluding VAT on Microsoft’s annual plan) bundles Exchange mailboxes, Teams and SharePoint that a perpetual licence cannot provide. AutoSoftKey supplies a Microsoft 365 Business Standard entitlement for one user at £89.95.

Where Office 2021 is clearly better

• One machine, no recurring bill. A home PC, a spare laptop, a bookkeeping machine or a Mac that just needs Word and Excel.
• Stability. Nothing changes under you: no new ribbon layouts, no features appearing mid-project, no forced move to the new Outlook.
• Offline and privacy-conscious use. The apps do not depend on an account being signed in and connected.
• Access and Publisher. Professional Plus includes both; Microsoft 365 Personal and Family do not include Access on Mac and are retiring Publisher.
• Cost. A pre-owned Office 2021 Professional Plus licence at £79.95 costs less than one year of Microsoft 365 Personal.

Which Office 2021 edition?

The Office 2019 and 2016 editions still install and activate but no longer receive security updates, so they suit offline or low-risk machines and legacy compatibility rather than a primary internet-connected PC. Office 2021 is the current one-off edition we recommend for everyday use.

About “lifetime” Office licences

Searches for a “lifetime” Office licence usually mean a perpetual licence like Office 2021: bought once, no expiry, no renewal fee. That is exactly what AutoSoftKey’s Office 2021 licences are — pre-owned perpetual licences transferred from previous holders, supplied with documentation and activation guidance. What does not exist is a lifetime Microsoft 365 subscription: Microsoft only sells 365 by the month or year, so any listing offering “Microsoft 365 lifetime” is either a shared account or something that will be revoked. Our guide to pre-owned software licences explains how the resale of perpetual licences works under UK and EU law.

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