If your device isn't one of the few to come with Microsoft Office pre-installed, it's highly likely you'll get a product key when purchasing the software.
That crucial information is required when installing it on your machine, and means you can reinstall it at any time should something go wrong. Some versions of Microsoft Office can even be installed on more than one device.
But what about if the worst happens and you lose your product key? Does that mean you can't reinstall office again?
Fortunately, all is not lost. Here's how to retrieve your Office product key via Windows.
How do I find my Office product key?
For recent versions (back to 2013) you can find the key in your Microsoft account. More details are available in our separate guide: how to download older versions of Microsoft Office.
If you're a bit of a techie, you may have thought to locate the product key by hunting through the Windows Registry. But this isn't possible as the code is encrypted. Luckily, there are plenty of apps that will do all the legwork for you.
Our favourite of these is ProduKey, a free app which will delve into the Registry to fish out and decrypt your Office product key, for versions older than Office 2013.
Once downloaded, run it and it will immediately display the product keys of any Microsoft Office software up to (but not including) 2013, as well as the keys of operating systems such as Windows Vista, 7 and 8. Then you can either copy the keys for future use, or export them to a HTML file and save it for future reference.
Although you're probably interested in finding only your Office product key, Recover Keys supports over 9000 apps, can scan remote Windows and Mac computers, recover license keys from external storage, scan multiple Windows installations, and can even run from a USB drive. And at £24.95 / $29.95, it's cheaper than buying another copy of Office.
How can I find an Office 2013, 2016 or 2019 product key?
If Office was pre-installed when you bought your PC or laptop, you might find a sticker on the machine itself with the code. But we're assuming you've looked in all those obvious places before turning to the web and finding this article.
Whether Office was pre-installed or not, here's the bad news: Microsoft changed how product keys are stored, so beginning with Microsoft Office 2013, only the last five digits of the 25-character code are stored in the Registry for Office 2013, 2016 and 2019.
What this means is that - as with all Windows 10 product keys - any code that a keyfinder app shows you will not work. If the first 20 digits are shown at all for an Office product, they will be generic.
The useful part, though, is that the last five digits should be the correct ones for your license which means you can search your email and computer's hard drive to see if you find any emails or matching files which contain the full product key.
If that fails, your remaining options are to do a full factory reset on your computer (but only if there is a recovery partition that includes all the original software that came with it) or to buy a new copy of Office.
However, if you weren't aware, there are a few excellent free office suites which work just like Microsoft's version and can save in the same formats, which means files you create with them can be opened and edited by others using Microsoft Office. See our recommendations for the best Office alternatives here.
If you need it, here's how to get the product key for Windows itself.