There are two types of activation methods for volume editions of Microsoft Office: Multiple Activation Key (MAK) and Key Management Service (KMS). If you have a system administrator, he or she can tell you which type of activation you must do. If you don’t have a system administrator, most likely you must activate by using MAK.
If you must activate by using MAK, you need to get or your administrator must give you a MAK key.
If you must activate by using KMS, you must ask your administrator for help with the KMS host or your computer.
Activate by using Multiple Activation Key (MAK)
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In Office LTSC 2021, Office 2019, and Office 2016, click File > Account > Change Product Key.
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Enter a MAK key.
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If you check the Attempt to automatically activate my product using the Internet box, complete the product key entry process.
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Restart your Office program.
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In Office LTSC 2021, Office 2019, and Office 2016, click File > Account.
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If you don’t check the box to activate automatically, you are asked to activate the next time you open an Office program.
Activate over the Internet or by phone
When you enter your valid product key, the Activation Wizard automatically runs and it gives you two choices on how to continue:
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Activate by using the Internet    The Activation Wizard automatically contacts the Microsoft activation servers through your Internet connection. If you are using a valid product key that has not already been used for the allowed number of installations, your product is activated immediately. When you activate through the Internet, your product ID, derived from the installation product key, and hardware information is sent to Microsoft, but this information is not used to identify or contact you. For more information, see the Privacy Statement. A response, the confirmation ID, is sent back to your computer to activate your product. If you choose to activate your product through the Internet and you are not already connected, the wizard alerts you that there is no connection.
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Activate by using the telephone    You can telephone an Activation Center and activate your product with the help of a customer service representative.
Important: Activation Center numbers aren’t listed in this article, because there are many numbers, and the correct number for you is based on several factors. You can get Microsoft software under various licenses, including individual retail licenses, original equipment manufacturer (OEM) licenses, and volume licenses. Telephone numbers vary by product license and country/region. In step 2 of the Activation Wizard, use the telephone number provided to call the Microsoft Activation Center. Telephone activation might take longer than activation through the Internet. You should be at your computer when you call, and you should have your software product key available.
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In the Activation Wizard, select the country/region where you reside and where you plan to use the product. The wizard provides one or more telephone numbers.
If you see the message Telephone activation is no longer supported for your product, you can ignore this error and call the numbers for your specific country/region listed in this article.
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Call the Activation Center. The customer service representative asks you for your installation ID, displayed on your screen, and other relevant information. After your installation ID is verified, you receive a confirmation ID.
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In the Activation Wizard, type the confirmation ID at the bottom of the screen, and then press Enter.
Note:Â Microsoft Text Telephone (TT/TTY) services are available for individuals who are deaf or hard of hearing. In the United States, using a TT/TTY modem, dial (800) 718-1599. From outside the United States, using a TT/TTY modem, dial (716) 871-6859. TT/TTY service is only available in English.
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Activate by using Key Management Service (KMS)
If you are using Key Management Service (KMS) activation, ask your system administrator for help. KMS activation occurs in the background. You don’t have to do anything to activate. The error code in the dialog box might provide a reason for why Office isn’t activated.
How can I tell whether my software has been activated?
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In Office LTSC 2021, Office 2019, and Office 2016, click File > Account > Manage Account.
What is Multiple Activation Key (MAK)?
A unique Multiple Activation Key (MAK) key is given to each organization for each volume edition of Microsoft Office. Each computer must then activate once with the activation servers hosted by Microsoft. Associated with each key is a count of the number of activations. For example, a MAK key for a Microsoft Office product with 100 activations allows the organization to install the same key on multiple computers and use up to 100 activations in total.
MAK is appropriate for organizations with computers that are not connected to the corporate network for long periods of time, such as portable computers. For this to work, a MAK key must be installed instead of the default KMS client key that is used in volume license editions of Microsoft Office.
With MAK activation, there is no requirement to periodically renew activation. You must reactivate if significant hardware changes are detected. In addition, you must request more activation allowances after the number of activations passes the predetermined limit. You have to manage the installation of MAKs and the potential need to manually activate systems by using a telephone when no Internet connection is available.
No functionality is lost even if the licenses for MAK clients cannot be renewed. Upon successful activation, users no longer receive notifications.
What is Key Management Service (KMS)?
Key Management Service (KMS) allows product activations on the local network. This eliminates the need for individual computers to connect to Microsoft for product activation. A computer is required to be configured as a KMS host. The administrator has to enter a KMS host key for the KMS host. The KMS host key has to be activated and connect once to Microsoft hosted servers for activation.
By default, the KMS client key has already been installed in volume editions of Microsoft Office programs. Computers running volume editions of Microsoft Office by using a KMS client key are called KMS clients, and they connect to an organization's KMS host to request activation. No action is required of the end user, and you do not have to enter a product key for KMS clients. The system administrator must activate the KMS host with Microsoft and configure the KMS host. The KMS client can also be configured for variable lengths of re-activation and renewal periods.
If a KMS client cannot activate, the end user sees a notification dialog box 25 days after installation of Microsoft Office. If a KMS client has been absent from the network for longer than 180 days after successful activation, the user sees unlicensed notifications and a red title bar when you start Microsoft Office. However, there is no functionality loss even if the licenses for KMS clients cannot be renewed. Upon successful activation, users no longer receive notifications.
The Microsoft Office KMS clients activate by connecting to a KMS host based on a client–server topology. KMS clients can locate KMS hosts by using Domain Name System (DNS) or by setting the KMS host name in the registry. KMS clients contact the host by using a remote procedure call (RPC). The activation process is invisible to the end user and does not require any interaction.
My product key isn't working
If your Office product key doesn’t work, or has stopped working, you should contact the seller and request a refund. If you bought a product key separate from the software, it’s very possible the product key was stolen or otherwise fraudulently obtained, and subsequently blocked for use. Unfortunately, there are many dishonest sellers who offer stolen, abused, or otherwise unauthorized Microsoft product keys for sale. Sometimes these product keys are printed on counterfeit labels or cards with a download link to Microsoft software, and sometimes they’re distributed with software media that is unauthorized for resale, such as promotional media, original equipment manufacturer reinstallation media, or other Microsoft program-specific media.
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