This article describes the process of deactivating of an Office installation on a device.

If a user tries to install Office from the Office 365 Portal, but the user has already installed and activated Office on five other computers then the following dialog is displayed during the Office installation:

Office 365 Exceeded Installations

To continue the installation of Office on this computer using the same user account, the user must deactivate an existing Office installation.  The user can select Deactivate one in the dialog box, which will take the user back to the Software page in the Office 365 Portal.  On the Software page, the user can select which Office installation to deactivate by selecting deactivate for the appropriate computer.  After the user selects deactivate, the following dialog box appears:
Office 365 Deactivation

After the user confirms the deactivation by selecting Yes, the user can return to the Choose your product dialog box, close the dialog box, and then continue with the Office installation. After Office is installed, the first time the user opens an Office application, such as Word, the user might see the following message:
Office 365 Application activation

The user should select Activate, and then when prompted, sign in to Office 365. This will activate the Office installation. After activation succeeds, the user will see the following message:
Office 365 Account Updated

Note: An Office 365 administrator can not see which computers a user has installed Office on. Only the user can deactivate an existing Office installation.

Deactivation doesn't actually uninstall Office from a computer. Office is still installed on the computer, but the Office applications are placed in reduced functionality mode.  When the user opens an Office application on a computer that has been deactivated, the user will see messages similar to this:
Office 365 Expired Software

Office 365 Expired Application