Change your Office product key
This article applies only to one-time purchases of Office 2016 or Office 2013, such as Office Home and Student, Office Home and Business, Office Professional, or individual Office applications.
Did you purchase multiple copies of Office and can only activate Office on the first computer? This can happen if you use the same Install button to install Office on multiple computers. Activation fails on the other computers because Office is using the same product key to activate on each computer. The only way to change the product key is to uninstall and reinstall Office on the computers where activation fails.To change the Office product key in a one-time purchase of Office
Uninstall the copy of Office that fails to activate. To do this, see Uninstall Office 2016, Office 2013, or Office 365 from a PC.
Reinstall Office by using the Install button for a one-time purchase that hasn't been activated. To do this, see Install Office on your PC or Mac.
Here's why it's necessary to uninstall and reinstall Office to change a product key
When you view your Office products on the My Office Account page, you'll see that each one-time purchase of Office has its own Install button. What isn't obvious is that each Install button is tied to a unique product key that's silently passed to Office during installation. This is why you aren't prompted for a product key when you activate Office.
You can view the product key for each one-time purchase of Office by clicking View your product key.
Tip: This is a different key than what's shown on your Office package or product key card.
To avoid accidentally installing the same product key more than once, we recommend that you create a list to track each one-time purchase of Office, its product key, and the computer where you installed Office. It's easier if you do this before you install Office, but you can create the list afterwards as well. To learn how to do this, see Manage multiple one-time-purchase Office installs that use the same Microsoft account.