Top-left, combined with your own branding.
While Brian is correct that companies want to have their own branding, putting only their branding there is bad for troubleshooting and supporting the end-user.
Though in some cases (apps distributed to the public) company branding gets prioritized over usability, this does not apply to back-end and B2B software. The end users are employees so there should not be any brand-loyalty problems. For example; when you sell a make-your-burger app to McD, Wendy's and BK, those companies could lose customers when they find out about the competition's apps. But when you sell an ingredient-inventory-app to those companies, you're not expecting employees to jump ship and try to work for the competition.
Even if you supply your customer with a (branded) set of documentation, the internet will still know more. When I google "view cpanel error logs", the first result... is not from the official site, but from a hosting provider. And that's a pretty common action.
However, your branding should be subtle, and the customer logo should be more prominent. You are working for them, your program is working for them, so the branding should indicate that relationship.