Office 2021 product key activation

If the Office 2021 key was already redeemed, it cannot be redeemed again under another Microsoft account; first restore the original account if possible, or contact Microsoft Support to verify the license if that account is permanently deleted.

1. Determine whether the key was previously redeemed

On the new laptop, open https://www.office.com/setup and sign in with a new or existing Microsoft account:

• If the key is accepted: It was unused. Enter the 25-character key without hyphens, complete redemption, install Office, and retain that Microsoft account for future reinstalls.
• If “This product key has already been used” appears: The key is already linked to the Microsoft account used for its original redemption. A redeemed key is no longer used for installation; the linked account replaces it for reinstalling and activating Office.^1^

Do not repeatedly try to associate an already-redeemed key with another account.

2. Try to reopen the deleted account

If the account is still within Microsoft’s 30- or 60-day closure grace period:

1. Go to https://account.microsoft.com.
2. Sign in with the deleted account.
3. Receive and enter the requested security code.
4. After restoration, open Services & subscriptions, install Office 2021, and activate it by signing in with that account.

After the grace period, or when an inactive account has already been automatically deleted, Microsoft states that the account can no longer be reopened.^2^

3. Transfer Office to the new laptop

For a retail one-time purchase such as Office Home & Student 2021 or Home & Business 2021, Microsoft permits transfer to another computer that belongs to you, generally no more than once every 90 days. Remove Office from the previous computer and do not retain another installed copy.^3^

If activation reports that the maximum number of activations has been reached, the documented transfer procedure requires activation through the perpetual-product activation process and removal of Office from the original computer.^4^ Since December 3, 2025, Microsoft has moved the traditional automated telephone activation workflow to its online Product Activation Portal.^5^

If the original account is permanently deleted

Contact Microsoft Support using a working Microsoft account and provide:

• The full 25-character Office 2021 key
• Purchase receipt or invoice
• Office edition, such as Home & Student 2021
• Seller information
• The old and new computer details
• An explanation that the Microsoft account associated with the license was deleted

Only Microsoft Support can determine whether ownership can be validated and the activation restored. A product key by itself does not provide a supported way to move an already-redeemed retail license to a different account.

If the key came preinstalled with the old laptop, was supplied by an organization, or is a volume/OEM key, retail-transfer instructions might not apply. For an organization-managed volume license, contact its IT administrator; for a problematic third-party key, contact the seller.^6^

References

1. Where to enter your Office product key | Microsoft Support
2. Reopen your Microsoft account | Microsoft Support
3. Transfer your Office license to another device or another person | Microsoft Support
4. Activate Office after reinstalling or installing on a different device | Microsoft Support
5. Activate Microsoft perpetual products using the Product Activation portal | Microsoft Support
6. [Office 2016 for Mac](https://support.microsoft.com/office/lifecycle/download-and-install-or-reinstall-office-2021-office-2019-or-office-2016#learn-more-about-product-keys,-workplace-discount-program,-and-volume-licenses)