How to link Windows 10 license to Microsoft Account in Windows 10 AU v.1607 and Later
Thanks to Digital Entitlement, Microsoft now give you a digital license for your Windows 10, as well as other Microsoft software, that you can save to the cloud, linking it to your Microsoft Account, so that whenever you fresh install Windows, the OS will get activated automatically.
If you use a Local Account to log in, your license may not get saved online. For this, you will have to specially take some steps to link the Windows 10 product license to your Microsoft Account. Let us see how you can do it in Windows 10 Anniversary Update v1607 and later.http://www.thewindowsclub.com/link-windows-10-license-microsoft-account