product key

Sign in on the other device with the Microsoft account linked to your Microsoft 365 subscription; you do not need a product key to install or activate Microsoft 365 on an additional device.^1^

Install and activate on the other device

1. Open the Microsoft account Services & subscriptions page:
   https://account.microsoft.com/services/
2. Sign in with the same Microsoft account used to purchase or redeem Microsoft 365.
3. Find Microsoft 365 and select Install.
4. Run the downloaded installer.
5. Open Word, Excel, or another Microsoft 365 app and sign in with that same account when prompted. The subscription should activate automatically.

Alternatively, visit https://m365.cloud.microsoft/apps, sign in, and select Install apps. Microsoft provides separate installation steps for Windows and macOS.^2^

If you cannot remember which account owns Microsoft 365

On the original device:

1. Open Word or Excel.
2. Go to File → Account.
3. Under the product name, look for the address shown after Belongs to.
4. Use that account on the other device.

Microsoft does not display the full product key inside Office or online; the associated account takes its place for activation and reinstallation.^1^

If this is not a Microsoft 365 subscription

If you purchased a one-time Office edition or have a new, unused key card, the process differs:

• Redeem a new key at https://www.microsoft365.com/setup.
• If the key was already redeemed, do not enter it again. Sign in with the Microsoft account used during redemption and install from that account.^3^
• If Office came through an employer’s Workplace Discount Program or is a workplace volume-license edition, obtain the key from the applicable workplace purchase record or contact the organization’s administrator.^1^

References

1. Using product keys with Microsoft 365 | Microsoft Support
2. Download, install, or reinstall Microsoft 365 or Office 2024 on a PC or Mac
3. Where to enter your Office product key | Microsoft Support