If you need to reinstall Office 2013 you will need the installation key but there is no way to view the key used. The key is visible if you login to your Microsoft account where you can view it.
This isn’t a problem if you only have one computer and key but many small companies they have many licenses rather than buying through the Open license program. Logging in here just shows you a list of licenses with no attribution to the computer.
Microsoft has made a note about how to get a hint at which key is used on a computer:
https://support.office.com/en-nz/article/How-to-find-your-Office-2013-product-key-after-installation-026bc81b-6b2f-4052-b433-f41e6cc31c5a
Find the Office 2013 product key associated with your PC
First, find the last five digits of the product key associated with your computer.
- Go to the PC that has Office 2013 installed
- Right click the Windows icon and select Command Prompt.
- Enter the appropriate command:For 32 bit Windows:cscript “C:\Program Files\Microsoft Office\Office15\OSPP.VBS” /dstatus
For 64 bit Windows:
cscript “C:\Program Files (x86)\Microsoft Office\Office15\OSPP.VBS” /dstatus
- The command prompt box will show you the last five digits of the product key associated with the installation on that PC.
- Make a note of the PC the Office 2013 product is installed on, and five digit number. You will need this for reference.
Once you have the last five digits, log into your Microsoft account and find the matching code.