If you installed Office on a PC as part of your Office 365 for business subscription, and your organization switches to a different Office 365 for business plan, you might have to install the version of Office that comes with your new plan. Office lets you know this by displaying the following message in Office in 1-3 days after your plan changes:

Note: We recommend that you uninstall your old version of Office first, and then install the version that comes with your new plan. Uninstalling Office doesn't delete your Office documents, but it's always a good idea to back them up first. You can skip the uninstall step, and immediately install the new version, but then you'll have both versions of Office installed, and some applications, like Access, might still be installed but show Unlicensed Product errors if you try to use them. You'll be prompted to uninstall Office 2016 if you try to install Office 2013.

Note: On the Office page, you might see the option to install Office 2016, Office 2013, or both. It depends on your new Office 365 plan and which versions of Office your administrator has enabled for you.