Microsoft 365 Product Key: Does Office 365 Use One, and Where to Find Yours (2026)

Reviewed 23 October 2026 by Esma, Technical Support Advisor at Nerdused.

Microsoft 365 does not use a product key in normal use. A subscription bought online is tied to your Microsoft account, and you install by signing in. A 25-character Microsoft 365 product key exists only on retail cards, and is used once at microsoft365.com/setup. One-time versions are different: Office 2019, 2021 and 2024 each come with a key, and the volume-licence Professional Plus and Standard editions we sell activate with it inside the app.

Microsoft 365, Office 365 and Office product keys at a glance

Product	Does it use a product key?	Where the key goes
Microsoft 365 Personal or Family (bought online)	No. The licence lives in your Microsoft account	Nothing to enter; sign in at account.microsoft.com
Microsoft 365 retail key card	Yes, once, to start or renew the subscription	microsoft365.com/setup (office.com/setup)
Office 365 Pro Plus 1-year account (Nerdused)	No key. You receive a ready-made Microsoft 365 account with its own login	Sign in at office.com with the credentials sent to you
Office 2024 Home, Home & Business (retail)	Yes, once, then the licence is in your Microsoft account	microsoft365.com/setup
Office 2024, 2021 or 2019 Professional Plus / Standard (volume licence, as sold by Nerdused)	Yes. The key activates the install directly with Microsoft	In any Office app: File > Account > Activate Product
Office preinstalled on a new PC	No printed key. A digital key is sent to the PC when Windows activates, if Office was paid for	Sign in; if Office shows a trial, no licence was included

Format: every Office and Microsoft 365 product key is 25 characters in five groups of five, XXXXX-XXXXX-XXXXX-XXXXX-XXXXX. Source: Microsoft Support, read 23 October 2026.

Do you need a Microsoft 365 or Office 365 product key?

Not if you bought it online. Microsoft says a digital Microsoft 365 subscription "doesn't require or provide a product key"; your Microsoft account does the job instead. That is why searching your PC for a "Microsoft 365 product key" or an "Office 365 product key" finds nothing. The only key you ever enter is under the silver foil on a Microsoft 365 card bought in a shop, and it is consumed when you redeem it.

The Office 365 Pro Plus 1-year account we sell needs no key either: the licence is pre-configured, so you sign in at office.com with the new account's own login and install the full desktop apps on up to five Windows, macOS, iOS and Android devices. The password can be changed; the email address cannot. It costs $29.99.

Where to find your Office product key, version by version

Office 2024 product key

Retail Office 2024 (Home, Home & Business): the key is on the card, in the Microsoft Store order email, or under Order History > Install Office. Once it is redeemed at microsoft365.com/setup, you reinstall by signing in. A Nerdused Office Professional Plus 2024 or Office Standard 2024 key is in our delivery email (search your inbox for "nerdused"), and support can re-send it.

Office 2021 product key

Most Office 2021 and 2019 retail versions no longer include a separate key, Microsoft notes: you sign in with the account linked to the licence. Our volume-licence Professional Plus 2021 keys are in the purchase email. Security updates for Office 2021 ended on 13 October 2026, but the apps keep working and activating (see our Office 2021 end-of-life guide).

Microsoft Office 2019 product key

Check the retail card, the Microsoft Store order history, or the seller's email for a Microsoft Office Professional Plus 2019 key. Office 2019 support ended on 14 October 2025, so a lost Office 2019 product key is a good moment to move to Office 2024. Key-finder tools will not help with any version from Office 2016 onward: Microsoft does not store the full key on the machine.

How to enter or change an Office product key

1. Retail Office 2024 or a Microsoft 365 card: go to microsoft365.com/setup, sign in with the Microsoft account you will keep, enter the key (without hyphens if asked) and follow the prompts to install.
2. Professional Plus or Standard (volume licence): install Office with the link in your email, open Word, go to File > Account > Activate Product and enter the key. If online activation is blocked, phone activation takes about five minutes. Install guides: Office 2024 Professional Plus, Standard 2024, Office 2021 and Office 2019.
3. Replacing a key on an existing install: File > Account > Change License, choose "Enter product key instead", enter the new key, select "Install this product instead", then close all Office apps. No button? Run Office updates first.

Which Office product key should you buy?

To pay once and use the desktop apps on Windows PCs, buy a one-time licence. Office Professional Plus 2024 is $29.99 for one PC ($49.99 for three), includes Access, and is supported by Microsoft until 9 October 2029. Office Standard 2024 is the same price without Access. Office Professional Plus 2019 is $24.99, the cheapest route to Publisher, but out of support. For a Mac, phone or tablet too, the Office 365 Pro Plus 1-year account above is $29.99. Compare them in our Office 2021 vs 2024 vs Microsoft 365 guide and Microsoft 365 subscription explainer.

Microsoft warns that keys sold separately can be stolen, fraudulent or blocked, and that if a key stops working you should contact the seller for a refund. Our 30-day refund promise covers exactly that. Every Nerdused key activates directly with Microsoft, and Nerdused is a member of the Microsoft Partner Program (ID 6467441). A Nerdused key is a licence for the PC it activates on, for the number of PCs shown on the option you choose.

Frequently asked questions

Does Microsoft 365 have a product key?

Only on retail cards. A subscription bought online is linked to your Microsoft account and has no key; you install by signing in.

Where do I enter a Microsoft Office 365 product key?

At microsoft365.com/setup (office.com/setup goes to the same place). Sign in, enter the 25 characters, and the subscription is added to that account. The key is not needed again.

How do I find my Office 2019 product key?

On the retail card, in the Microsoft Store order history, or in the email from the seller. Office does not display the full key, and key-finder tools cannot recover it for Office 2016 or later.

Can I reinstall Office without the product key?

Microsoft 365 and retail Office: yes, sign in at account.microsoft.com and install from Services & subscriptions. Volume-licence Professional Plus and Standard: you need the key again on the same PC, so keep the delivery email.

Why does my key say "already used"?

For Microsoft 365 or retail Office, the key was redeemed and the licence is in the Microsoft account that redeemed it; sign in with that account. A volume-licence key activates on the number of PCs you bought, no more. An unused Nerdused key that will not activate is replaced or refunded within 30 days.

Is a cheap Office product key genuine?

Volume-licence Professional Plus and Standard keys are cheap because they are delivered digitally with no box or retail margin; the apps are the same. Buy from a seller that activates with Microsoft, gives a refund promise and can be contacted.

Can one Office product key activate two PCs?

A one-PC key activates one PC. For more, buy the 3-PC or 5-PC option of Office Professional Plus 2024 or Standard 2024; each PC activates with the same key. The Office 365 Pro Plus account covers up to five devices with one login.

Sources: Microsoft Support, Using product keys with Office; Where to enter your Office product key; Change your Office product key. Prices read from nerdused.com on 23 October 2026.