where can I buy Qty12 Windows 10 licenses?

you can check on amazon.com

https://www.amazon.com/Microsoft-Windows-10-Pro-Download/dp/B01019BOEA

all the  best

Is there a reason you don't want to buy it directly from Microsoft?  https://www.microsoft.com/en-us/store/b/windows?activetab=tab%3ashopwindows10

Any Microsoft partner can sell you licenses if they so chose.  I routinely sell licenses to my clients.  You can also get them from Dell, NewEgg, Micro Center, CDW, and any major IT vendor.

You need retail version or for a business, you want each to come with its own key. Or for business to have a single volume license?
Are you upgrading from an existing Windows 7,8?
Or you need OEM versions where you are building a system and selling them?

Thank you all for your input. Perhaps I should have been more specific. I think Arnold's questions highlight the differences in "strategies" with the licensing that I didnt give enough information on. Sorry about that.  I am actually looking to be able to license them all under a single key. This is for a non-profit organization and they will all be upgrades for either Win 7 or Win 8.

newegg.com has an open license win10 pro upgrade for $170

IMHO, you shoukd reachout to Micòsoft directly and see whether the organization qualifies for discounts, if not outright ....