We're unable to determine the location of the server, which holds your data, James. Rest assured, all your company's information is securely protected by the system.
To start with, QuickBooks uses AWS (Amazon Web Services) for its hosting needs, utilizing a cloud computing platform. Data security is a top priority as we understand that data is one of your company's most valuable assets, and we take huge measures to ensure its protection.
To learn more about how we securely protect your data, you may check out this article: Privacy and security in QuickBooks. (Please note that while this article is based on practices from another region, but the main ideas still apply).
I've also attached this resource to learn how to manage your account's permission which can be assigned to a different user on their roles: User roles and access rights in QuickBooks Online.
You can always drop by again to this thread once you have more questions about your data in QuickBooks. Our team is always available to help you.