Buying Office once, or renting it
There are two different products behind the word Office. A perpetual version — sold with a year in its name, such as Office 2021 or Office 2024 — is bought once and keeps working indefinitely on the version you bought. It does not gain features later and it does not follow you to a new major release.
Microsoft 365 is a subscription. It updates continuously, includes cloud storage, and covers several devices, and it stops working as an editing tool when the subscription lapses — your files remain, and the apps drop to a read-only state.
The decision is not really about price per year. It is about whether you want the newest version in three years' time. Someone writing letters and spreadsheets is well served by a perpetual licence bought once; someone who needs current collaboration features is buying a subscription whether they like the model or not.
The edition names, and the one that dominates cheap listings
The consumer perpetual editions are Office Home and Office Home & Business. Home covers Word, Excel, PowerPoint and OneNote; Home & Business adds Outlook and the right to use the apps commercially. Microsoft renamed Home & Student to simply Home with the 2024 release, so both names appear in listings depending on which version is being sold.
Professional Plus is not a consumer edition at all — it is the volume-licensing SKU sold to organisations under agreements, and that is why it appears at prices the consumer editions never reach. These keys frequently activate, and they are also the licences most exposed to later withdrawal, because they were issued against an agreement neither you nor the seller is a party to.
Read the platform and the device count too. Some listings cover one PC, some several; some are Windows-only where the buyer assumed a Mac was included.
The account owns the licence
Perpetual Office and Microsoft 365 both redeem against a Microsoft account, and after redemption that account is where the entitlement lives. Reinstalling later means signing in, not finding the key again.
Redeem to an account you control personally and expect to keep. A licence redeemed to a work address or a throwaway mailbox is a licence you may not be able to reinstall in two years, and the key will not redeem a second time to fix that.
A Microsoft 365 code adds time to a subscription rather than starting a parallel one, and there is a limit to how far ahead a subscription can be extended. How a code for one plan behaves on an account holding another — Personal against Family, say — depends on the plan and the market, and it is decided at redemption rather than by you. Check the plan and the remaining term before buying more time.
What a perpetual licence stops getting
A perpetual version keeps working indefinitely, but Microsoft supports each release for a defined period, and once that ends it stops receiving security updates. The software does not switch off — it simply stops being patched, which matters most for a program that opens documents other people send you.
That end date is published years in advance, and it is the number to check before buying an older release cheaply. A 2019 licence at a large discount may have considerably less supported life left than a 2024 one at a modest premium, and the per-year arithmetic often favours the newer version once you account for it.
The file formats are stable across releases, so an older version is not an isolation problem in the way it once was. Support lifetime, not compatibility, is the thing worth paying attention to.
The family plan changes the arithmetic
Microsoft 365 sells a family tier covering several people, each with their own sign-in, their own storage allocation and their own installs. Split across a household it is frequently cheaper per person than the single-user plan, and considerably cheaper than several perpetual licences.
The people you share with need their own Microsoft accounts, and each of them holds their entitlement through the organiser's subscription rather than owning anything. If the organiser stops paying, everyone drops to read-only at once, which is worth agreeing before rather than discovering after.
It is also the reason to be precise about which plan a listing is for. Personal and Family are priced differently and cover different numbers of people, and a code bought on price alone may not be the plan the household actually needs.
Installing without tripping over the old one
Office installations do not always coexist. Installing a perpetual version on a machine with an active Microsoft 365 subscription, or the reverse, can leave the apps confused about which licence they are running under, and the symptom is usually a persistent sign-in prompt rather than an error that names the problem.
The clean path is to remove the previous installation first, then install fresh and sign in. Microsoft publishes a support tool for removing an installation that will not uninstall normally, which is worth reaching for before assuming a new key is faulty.
Before you buy
Decide perpetual or subscription first, because it changes which listings are even relevant. Then confirm the edition against the consumer names, the platform, and the number of devices. Confirm what you are buying is a key rather than an account login.
If you are buying subscription time, check the plan matches the one on the account and that the term has room to extend. That single check prevents the most common irreversible mistake in this category.
