Companies have to be registered companies and have between 5 and 249 employees.
Apparently this does not apply to bespoke software and it has to be the first time of purchase. As Dan 55 comments, does this cover subscriptions?
I have a customer who paid a few thousand for some off the shelf software some years ago. There is a new version out which he is interested in upgrading to, but this scheme is almost encouraging him to go to a rival product, buy that and ditch the existing one.